This week, we shall continue the study of the book of Jeremiah in the
Old Testament.
The division of chapter 31 is based on the assumption that as 31:1 refers to the restoration of “all the families of Israel”, the focus of 31:2-22 appears to be on Samaria, the kingdom of Israel (see K&D, 270)—the ten tribes who were in exile for a longer period, and the focus of 31:23-26 is on Judah.
30:22-31:1—God’s Wrath Has a Purpose
30:22 and 31:1 serve as an “inclusio” to emphasize their restoration to being “God’s People":
(1) What then has God’s wrath to do with such a restoration? (30:23-24)
(2) Why was it hard for the people to understand then? (30:24)
(3) What is God’s ultimate purpose? (31:1)
31:2-6—Restoration of Israel (I)—The basis of restoration
(4) Why would God care to restore those He punishes? (31:3)
(5) Where will the remnant of Israel be found by God and given rest? (31:2)
(6) Apart from joy, dancing and planting of vineyards, what is the significance of the watchmen on the hills of Ephraim calling upon people to the Lord in Zion? (Ephraim represents the Northern Kingdom which used to have their people worship in Dan and Bethel before—see 1 Ki. 12:28-29) (31:6)
31:6-9—Restoration of Israel (II)—Those who will return
(7) From where will the remnant of Israel be returned? (v. 8)
(8) Who will be among those being brought back? What does it serve to portray?
(9) How will they be brought back? (v. 9) Why?
31:10-14—Restoration of Israel (III)—A bountiful restoration
(10) Why does the Lord call upon the nations to proclaim the restoration of Israel? (v. 10)
(11) The restoration is made possible by “ransom” and “redemption”: What ransom has been paid for their restoration? (Heb. 9:15)
(12) How meaningful is this promise of a bountiful restoration to those in exile and to Israel today?
31:15-20—Restoration of Israel (IV)—Weeping no more
(13) While during the destruction of Jerusalem (and other times of tribulation like the Holocaust), no doubt many Jewish women wept for the loss of their children, but the ones mentioned in v. 15 specifically relate to the mothers in Ramah:
a. What is it referring to? (see Matt. 2:18)
b. How does the weeping in Ramah contribute to the comfort of the weeping mothers in Israel? (vv. 16-17)
(14) In this process of restoration, apart from the unfailing love of God (31:3), what part does Ephraim, (i.e. Israel) play as well? (31:18-19)
(15) How does 31:20 reveal the purposes of God’s heart? (see 30:24)
31:21-22—Restoration of Israel (V)—Call to action
(16) The urging of the people to put up road signs signifies that God is ready to bring them back, except that these things take place:
a. They need to do their part: What is it? (vv. 21-22) and
b. God will do His part: What is it? (v. 22—see Note below)
(17) What is the main message to you today and how may you apply it to your life?
Note:
“Older expositors almost unanimously took the verse to predict the virgin birth of the Messiah. Their arguments are (1) The ‘new thing on earth’ would require an event of unprecedented character. (2) the word, ‘create’ implies an act of divine power. (3) the term ‘woman’ demands an individual rather than an entire nation. And (4) the word ‘man’ is properly used of God (Isa. 9:6).” (C.I. Scofield)
“The fierce anger of the Lord will not turn back until He fully accomplishes the purposes of His heart. In days to come you will understand this.” (Jer. 30:24)
Even though the Lord foretells through Jeremiah both His severe judgment of Israel and their restoration in the future, He does not expect Israel to understand. Just like a child being disciplined by his father, at the time of discipline, the Bible says, “No discipline seems pleasant at the time but painful” (Heb. 12:11). He would not have ears to hear that the discipline will produce the fruit of righteousness in him.
Still the Lord bares His soul to tell them that the judgment is necessary in order to achieve “the purposes of His heart” (30:24) and His heart is one of a loving father who holds His son dear, who delights in him and in spite of often speaking against him, He still remembers him and in fact, His heart yearns for him and has great compassion for him in his suffering (31:20).
Unfortunately, as we know, Israel really did not understand His heart, and still does not. However, are we any better than Israel, when we come across hard times or when things do not go our way? Do we not fret and complain? Do we not quickly ask, “Why” or “Why me”? Do we not even decide to do something foolish to hurt ourselves or hurt His heart?
Therefore, we should always remember this promise of God: “In days to come you will understand this” (30:24) and we should also remember that He has loved us “with an everlasting love” (31:3) and His plan is never to harm us, but to prosper us and to give us hope in the future (29:11). This is the heart of God, because He is our Heavenly Father (Matt. 6:9).
31:23-28 (In prose form)—Promise of Restoration to Judah
(1) When God brings back His people to
Judah, what kind of a picture is depicted in vv. 23-25, especially with the
references to the following?
a. Righteousness and sacredness
b. The living “together” of all peoples, farmers and shepherds in particular
c. The refreshing of the weary and the faint?
(2) 31:26 is a difficult verse, as we do not know exactly know who is speaking:
a. If it is the prophet, what does it mean?
b. If it is the Lord, what does it mean?
(3) The restoration extends to the uniting of Israel and Judah (v. 27)
a. How does the Lord use their horrific experience of suffering to guarantee their restoration?
b. What does “to watch over” mean? (v.28)
31:29-34 (Back in poetic form)—A New Beginning
(4) Obviously, God has always judged people by their own sins. What then is new about their saying and why, i.e. what has changed? (v. 29; see Ezek. 18:2, 25 as well)
(5) Promise of a New Covenant (vv. 31-34)
a. Why is a new covenant needed? (v. 32)
b. How different is the new covenant from the old? (v. 33; see 2 Cor. 3:3)
c. How can the new one be written in their minds and hearts?(v. 34)
d. What is the result of knowing God? (v. 34)
31:35-40—The Certainty of Restoration
(6) What does the Lord use to guarantee the rebuilding of Israel? (vv. 35-36)
(7) What does the Lord use to assure them of their forgiveness? (v. 37)
(8) Given these assurances, how would you look at the future of Israel and world history?
(9) Some of the places mentioned in vv. 38-40 are not known:
a. What idea is intended by vv. 38-39?
b. What is the idea behind v. 40? (The valley of dead bodies is likely the place referred to more than once by Jeremiah as the scene of pagan cult practices, as in 2:23; 7:31; 19:2ff etc.)
(10) What is the main message to you today and how may you apply it to your life?
“ ‘The days are coming,’ declares the Lord, ‘when I will make a new covenant with the people of Israel and with the people of Judah'.” (Jer. 31:31)
In His detailed promise for restoration not only of Judah, but also of Israel, the Lord points out that the basis of this restoration rests in the making of a “New Covenant” with them.
The logical questions are these:
- What happened to the Old Covenant?
- Why would the New Covenant work?
The answer is given in 31:32-34 in that the Old One that God established with their ancestors when He “took them by the hand to lead them out of Egypt” (31:32) has been broken by them, obviously through their worship of idols and other deeds of wickedness. And, as the Apostle Paul points out, the Old Covenant was written on “tablets of stone” (2 Cor. 3:3) that can only make known our sin (Rom. 7:7), but is incapable of changing our hearts and minds. Thus a New Covenant that is written on our minds and hearts is needed.
However, how then can the New Covenant be written in our minds and our hearts? The answer is this: By knowing the Lord (31:34). We understand that the word “know” in Scriptures points to experiential knowledge, and not just objective knowledge (e.g. Genesis 4:1). Therefore to know God is to establish a personal relationship with Him, and that is made possible by receiving Jesus Christ who has established this new Covenant in His blood (1 Cor. 11:25) into our hearts as our personal Lord and Savior. As a result, not only are our sins forgiven (31:34), but we will become children of God (Jn. 1:12) and will even inherit Everlasting life (Jn. 3:16).
This is considered the second part of the “Book of Consolation”. It is mainly written in prose form and centers on the purchase of a field by Jeremiah at the time when Jerusalem was under siege (see Note below).
32:1-16—The Purchase of Land
(1) What was the reason given for Jeremiah’s arrest? (vv. 3-5)
(2) What’s wrong with Jeremiah’s prophecy as far as the king was concerned? (see 2 Chr. 36:12-13 as well)
(3) Why would Jeremiah’s uncle want to sell his land? (v. 6)
a. Why would he want to sell at a time of siege?
b. Who in his right mind would buy land at a time like this?
(4) Why did Jeremiah oblige? (v. 8)
a. What was the reason for putting the purchase documents in a clay jar?
b. What is the message behind it? (v. 15)
32:17-25—The Prayer of Jeremiah: As much as he submitted to the word of the Lord, the prayer that followed shows his struggle in making such a decision. Consider what yet followed:
(5) Jeremiah opened his prayer with adoration and praise (vv. 17-19)
a. How did he acknowledge who God is and His majestic power?
b. How did he acknowledge the ways and purposes of God’s actions?
(6) Not only did Jeremiah acknowledge God’s power and His ways in general, but he also recounted what God had done for Israel (vv. 20-22):
a. What has the Exodus experience meant to the world? (see Jos. 2:9-11)
b. What has the Exodus experience meant to Israel?
(7) The present demise of Judah (32:23-25)
a. How did Israel reciprocate the majestic power and love of the Lord for them? (v. 23)
b. What is the result of their disobedience and their present demise? (vv. 23-25)
(8) How did v. 25 show that Jeremiah was struggling with God’s command to buy the field? The K&D translation based on the original Hebrew is “and yet Thou sayst to me” (K&D, 292).
(9) Since he did have doubts about this decision, why then would he buy the field?
(10) What is the main message to you today and how may you apply it to your life?
Note:
“The siege had begun in the ninth year of Zedekiah (39:1; 52:4) and was afterward raised for a short time, in consequence of the approach of an auxiliary corps of Egyptians, but as soon as these had been defeated, it was resumed (37:5, 11) … Not till during the temporary raising of siege, when he (Jeremiah) wanted to go out of the city to the land of Benjamin, was he seized and thrown into a dungeon, on the pretence that he intended to go over to the Chaldeans. There he remained many days till King Zedekiah … ordered him (37:11-24) to be taken into the court of the prison house … where he remained in confinement till the city was taken (38:13, 28; 39:14).”
(K&D, 288)
“And though the city will be given into the hands of the Babylonians, you, Sovereign LORD, say to me, ‘Buy the field with silver and have the transaction witnessed'.” (Jer. 32:25)
As I was brought up as a young Christian, I often heard sermons that praised the faith of the saints in the Scriptures. That made me feel like a loser every time I saw myself struggle over instant obedience to the Word of God or the prompting of the Spirit. Seldom had I heard sermons that depict the struggles of the saints as a normal human being. Maybe it was not the preacher's fault; maybe it was my own fault in not realizing that even for the saints in the Bible, they also often struggled in their faith, especially in the face of illogical or unreasonable commands by the Lord. Jeremiah’s struggle over the command to purchase the piece of land from his uncle is a case in point.
We are not told why his uncle, all of a sudden, felt the need to sell his land of inheritance, especially at the time when the city of Jerusalem was under siege by the Babylonians. Maybe, the siege had begun to lead to famine and his uncle had to sell the land in order to survive. In any case, under the Leviticus Law (Lev. 25:25), Jeremiah was obliged to buy it. Still he struggled with the decision; but since the word of the Lord came to him foretelling such an event, he knew it was of the Lord and obeyed accordingly.
However, it does not mean that he did not have doubt about not only his decision, but also why God would make him do it at a time like this, because once the Babylonians came in and destroyed the city which was guaranteed to happen according to the word of the Lord, all properties in Judah would lose value and basically be worthless! (2 Ki. 25:12)
Through the prayer of Jeremiah, we can learn a valuable lesson on how we might overcome our doubts and submit to the will of God.
Jeremiah did not open his
prayer by
confronting God right away with why He would ask him to buy the land at
such a time, but he opened his prayer, like most of the Psalmists did in
the
Psalter in this way:
- Adoring God for Who He is—the Maker of the heavens and the earth, the Lord Almighty (32:17-18);
- Praising God for His ways and purposes—who shows love to thousands (who belong to Him) and brings punishment on the wicked (32:18-19);
- Remembering the signs and wonders He performed for His people, delivering them from their slavery in Egypt and bringing them into the land they now possessed.
As much as he ended his prayer still with the question of why God would command him to buy the land, his question is not so much a challenge in disobedience, but a question that follows submission, because he had reminded himself that God is the Almighty God and there is nothing too hard for Him (32:17) and that He always acts with purposes marked by His righteousness and love.
Therefore such a question which is marked by praise and followed by submission will not displease the Lord, but would certainly receive an answer from the Lord (32:26ff).
This is God’s reply to Jeremiah’s prayer concerning the purchase of his uncle’s land:
32:26-27—Preface to God’s Answer
(1) How does the Lord preface His answer? (v. 27) Didn’t Jeremiah say the same in his prayer already? (v. 17)
32:28-35—The Affirmation of Destruction
(2) What will happen when the city is captured by Nebuchadnezzar? (v. 29)
(3) Why? (v. 29)
(4) Can you count how many times the word “anger” is mentioned by the Lord?
a. What is the reason for the first anger? (v. 29)
b. What is the reason for His 2nd anger? (v. 30)
c. What is the result for arousing His anger? (v. 31)
d. Who were the ones that have provoked Him to anger and what have they done? (vv. 32-35)
32:36-41—And Yet
(5) What does God promise after their captivity? (v. 37)
(6) The Lord had previously declared that Israel would be His people and He their God (Leviticus 26:12). How different will this be upon their return from captivity in the following aspects?
a. Their fear of Him (v. 39)
b. Their children (v. 39)
c. God’s attitude towards them (vv. 40-41)d. Ensuring that they will not turn away (v. 40)
e. Permanency of dwelling (v. 41)
(7) How does God frame (or call) this promise? (v. 40)
32:42-44—Answer to the Question of Land Purchase
(8) In promising: As great as the calamity has been, so great the prosperity will be (v. 42):
a. What will the land be like at the destruction by Babylon? (v. 43)
b. What is God’s promise concerning the land in the future? (v. 44)
(9) What then is God’s answer to Jeremiah? (The land that he bought from his uncle in Anathoth is in the territory of Benjamin.)
(10) What is the main message to you today and how may you apply it to your life?
“'Fields will be bought for silver, and deeds will be signed, sealed and witnessed in the territory of Benjamin, in the villages around Jerusalem, in the towns of Judah and in the towns of the hill country, of the western foothills and of the Negev, because I will restore their fortunes', declares the LORD.” (Jer. 32:44)
It appears that Jeremiah did have some hesitation in purchasing the land of his uncle. While he was the nearest relative, should he decline to purchase it, I believe there would be others next in line (in terms of relations) to purchase the land. If such was not the case, he would not even have room for hesitation.
His hesitation obviously had to do with the fact that under a siege, the land within Judah would not have much worth, not to mention that he knew for sure that the land would be seized and be completely destroyed by the Babylonians. That meant that whatever he purchased, at however low a price, would be worthless.
His hesitation was met with a lengthy answer from the Lord, which in essence, on the one hand, affirmed the destruction of the land by Nebuchadnezzar, but on the other hand assured the return of the captives and prosperity to the land. It would be to the point that “Fields will be bought for silver” again, and that would include the territory of Benjamin where the piece of land purchased by Jeremiah was situated (32:44).
However, the reality is that, all these things would not happen for at least another 70 years. By then, Jeremiah would have passed away, and as we learn from the books of Ezra and Nehemiah, the land of Judah would remain very sparsely populated and subjected to poverty still for many years to come. In other words, Jeremiah would not be able to recover his investment, not only in his life time, but also in the many years that followed for his descendants.
However, the fact that he purchased this property did serve as a powerful message to the people: It backed up this prophecy of return by the Lord and God’s unwavering commitment to restore Israel. It was, after all, a small price to pay for the sake of ministry.
While Jeremiah was still held in the courtyard of the guard, after his first prayer was answered, the Lord spoke again, re-iterating His promise of restoration of Israel:
33:1-4—The Invitation to Call
(1) Why does the Lord encourage Jeremiah to call to Him?
(2) What great and unsearchable things is He talking about?
(3) In this invitation to call, how does the Lord address Himself? Why?
(4) What has happened at the time when the city was under siege?
(5) Would such an invitation be extended to us? Why or why not?
33:5-9—The Reiteration of Promise of Restoration (I)—This promise is made against the backdrop of dead bodies filling the city, and yet the Lord these promises:
a. Health and healing (v. 6)
b. Abundant peace and security (v. 6)
c. Rebuilding upon return from captivity (v. 7)
d. Cleansing and forgiveness of sins (v. 8)
e. The bringing of renown, joy, peace and honor to the Lord by the city (v. 9)
f. Nations will be in awe and tremble at the above (v. 10)
(6) How would the survivors or captives feel at the sight of a city filled with dead bodies?
(7) What would such a message mean to them (should they recall or read it again)?
(8) Which of the above promises in the restoration should mean the most to them?
(9) How does this promise reveal the heart of God for His people?
33:10-13—The Reiteration of Promise of Restoration (II)—This promise is made against the backdrop of a desolate city, void of people and animals!
(10) How would the survivors or captives feel at the sight of a city void of people and animals?
(11) What would such a message of joy and gladness mean to them?
(12) How does this promise reveal the heart of God for His people?
(13) What would such a message of pastures re-inhabited by shepherds and flocks mean to them?
(14) How does this promise reveal the heart of God for His people?
(15) What is the main message to you today and how may you apply it to your life?
“Call to me and I will answer you and tell you great and unsearchable things you do not know.” (Jer. 33:3)
Commentators have wrestled much with the reason for the Lord to invite Jeremiah to call to Him and also that it seems “strange that, though in the opening part the prophet is promised a revelation of greater, unknown things, for which he is to call on God, yet the succeeding announcement contains scarcely anything remarkable or peculiar” (Hengstenberg).
Because chapter 33 is clearly connected to
the previous chapter by the reference to the fact that “Jeremiah was still
confined in the courtyard of the guard” (33:1), it is obvious that
“‘Call unto me,’ etc. is occasioned by the prayer of the prophet, 32:16-25. To this prayer the prophet had received an answer, 32:36-44; but he is here admonished to approach the Lord more frequently with such a request. The God who has the power to execute as well as make decrees is quite prepared to given [sic] him an insight into His great thoughts regarding the future; and of this a proof is at once again” (K&D, 296).
Since this invitation is connected to his
previous prayer and since Jeremiah was still in prison, it is not far-fetched
to imagine that the prophet’s mood was quite subdued for these reasons:
- The city was under siege and would be totally destroyed in an instant.
- The King was determined to ignore his message, and total destruction and death of many seemed not only unavoidable but imminent.
As a prophet who deeply loved his people, whatever future promises that God has spoken through him could not have meant too much at this time. Not that he did not believe in the oracles of the Lord, but the present was just too much to bear and behold.
I believe,
it was this struggle of Jeremiah that the Lord deeply cared about, and if you
read the content of this part of God’s oracle, it was meant primarily for the
prophet only and secondarily to the people. Thus what was revealed to him, was nothing short of “great and
unsearchable". Consider the following:
- Against the backdrop of a city filled with slain, dead bodies is the promise of health, healing, peace and security. More than that, beyond these external blessings is the promise of spiritual restoration with the cleansing and forgiveness of sin. But the greatest and unsearchable part of this promise is that God Himself will be honored and praised, and that all nations on earth will be in awe and even tremble at the sight of the restoration of Israel (33:9).
- Against the backdrop of a desolate city void of people and animals is the promise not only of sounds of joy and gladness, but voices of worship, the singing of Psalm 136 in the temple of Lord. But more than that the fulfillment of all these promises, as pointed out in v. 15 (to be studied in tomorrow’s devotion), all is based on the Righteous Sprout of David, the Lord our Righteous Savior. While we now understand Who He is—none other than the Only Begotten Son of God who became a man and died as the atoning sacrifice for Israel and all humankind, if Jeremiah knew and understood it at the time, would it not be the greatest and most unsearchable thing to him that would only make him bow in worship?!
The Basis of the “great and unsearchable things” concerning the promise of restoration of Israel is being foretold:
(1) According to vv. 14-16
a. What is the basis of the fulfillment of the good promise God made to the people of Israel and Judah?
b. From whose line would this Branch come from?
c. What is He called?
d. How does our Lord Jesus Christ fit these descriptions? (See Matt. 1:1; 1 Pet. 3:18)
(2) According to vv. 17-18, what can you conclude?
a. What two roles would this Righteous Savior assume?
b. We know that the Lord Jesus is the King of Kings, but in what ways is He also our priest? (see Heb. 7:20ff; 10:12)
(3) According to v. 22:
a. What promise is made concerning the descendants of David and Levites?
b. How is it fulfilled in us today? (see 1 Pet. 2:9)
(4) How firm and certain is this new covenant with David and the Levites? (vv. 20-21)
(5) What is the backdrop to His promise not to reject the descendants of Jacob and David? (v. 24)
(6) Whom does the Lord reiterate as the one who will rule over the descendants of Abraham, Isaac and Jacob? (v. 26)
(7) What is the main message to you today and how may you apply it to your life?
“I will make the descendants of David my servant and the Levites who minister before me as countless as the stars in the sky and as measureless as the sand on the seashore.” (Jer. 33:22)
Yesterday we were considering how some commentators think the revelation by God to Jeremiah in chapter 33 is “scarcely anything remarkable or peculiar”. We have already refuted this view by pointing out that the promise of a Righteous Savior who is a Sprout from David’s line is already unthinkable, because it points to the incarnation of the Only Begotten Son of God who will die as an atoning sacrifice for not just Israel, but all humankind. If this is not something great and unsearchable, what is?!
But the greatness and unsearchability of this revelation does not stop there, because as much as the focus appears to be the restoration of Israel and Judah, this salvation, in fact, this Savior belongs to all peoples. As a result, while v. 22 speaks of the promise that God will “make the descendants of David my servant and the Levites who minister before me as countless as the stars in the sky and as measureless as the sand on the seashore” (33:22), we have seen its fulfillment already in our age and in us. The descendants of David speak to the royal line, while the descendants of Levites refer to the priests who serve before the Lord. The Apostle Peter points out that because of the disobedience and disbelief of Israel, we who have believed have become “a chosen people, a royal priesthood, a holy nation, a people belonging to God” (1 Pet. 2:9).
Yes, the unthinkable has happened. We who once were not a people are now the people of God; once we had not received mercy, but now we have received mercy (1 Pet. 2:10). As a result, even now, “the descendants of David my servant and the Levites who minister before me” are “as countless as the stars in the sky and as measureless as the sand on the seashore” (33:22), to the glory and praise of the Lord!
34:1-7—Message to Zedekiah of Imminent Captivity
(1) Based on vv. 1, 6-7, what was the timing of this prophecy to King Zedekiah?
(2) What is the first part of the message in vv. 2-3? What does the Lord expect Zedekiah to do?
(3) What is the second part of the message in vv. 4-5? How would you respond to it if you were Zedekiah?
(4) What do you think Zedekiah’s response to the news was?
34:8-22—Reneging on the Covenant to Free Slaves
The second event took place when the Babylonians temporarily withdrew from Jerusalem upon the news of the approaching Egyptian army under Pharaoh Hophra (in the late spring or early summer of 588 B.C.; 44:30):
(5) Since the “ancestors” did not care to honor the requirement to free Hebrew slaves every 7th year (34:14), according to the stipulation in Deuteronomy 15:12, what might have motivated King Zedekiah to do such a noble act to repent, ordering everyone to enter into a covenant to free their slaves? (vv. 8-10)
(6) What is the provision concerning Hebrew slaves in the Law of Moses? (See Deut. 15:12; and vv. 12-14)
(7) Why had their ancestors not been honoring this law? (v. 14)
(8) Does the king’s motivation have anything to do with the forgoing message of the chapter and the inevitable fall of Jerusalem? (See Note 1 below concerning this covenant ceremony.)
(9) How did the Lord look upon their action? (v. 15)
(10) What might have happened that caused the people to renege on the covenant? (v. 11)
(11) Did it have anything to do with what happened as described in v. 21? (see Note 2 below)
(12) How did the Lord look upon their action now? (v. 16)
(13) Based on the way the Lord is going to judge them (vv. 17-18), which was the sin that invited this form of punishment: Not freeing slaves or their violation of the covenant made in the house that bears the name of the Lord?
(14) As Part of His punishment, what will God do with the army of Babylon that had retreated? (v. 22)
(15) What is the main message to you today and how may you apply it to your life?
Note:
“Recently you repented and did what is right in my sight: Each of you proclaimed freedom to your own people. You even made a covenant before me in the house that bears my Name.” (Jer. 34:15)
It is surprising and also refreshing to learn that King Zedekiah took the initiative to engage the people, notably the nobles, to enter into a covenant before the house of the Lord to free all their Hebrew slaves. “The Hebrew text spells out the details (that) everyman to send away free his male slave and every man his female slave” (NICOT, 610).
We should not doubt his sincerity, as the Lord took it as a sign of repentance, and commended him for doing the right thing (v. 15). Since it was a sincere act, one has to assume that both the words of warning from Jeremiah (likely the message in the beginning of the chapter) and the fact that he saw no hope of fending off the mighty army of Babylon had caused him to humble himself to repent, hoping that God might relent as He had previously said repeatedly (18:8; 26:3, 13; 26:19).
The question is this: Why did he and the nobles so quickly change their minds?
I am afraid it has to do with the retreat of the Babylonian army mentioned in v. 21. Upon the approach of an Egyptian army under Pharaoh Hophra probably in the late spring or early summer of 588 B.C., the Babylonians had no choice but to temporary lift the siege of Jerusalem and went to meet the Egyptians (see NICOT, 606). That created a false hope on the part of King Zedekiah and his people, thinking that perhaps the Egyptians could come and deliver them and if so, to free these slaves would mean a substantial loss in property. The “Lachish Letter III” (mentioned in our note appended to the reflection questions) serves to prove this point.
I believe the Lord was so enraged not primarily because they did not free their slaves, for their ancestors hadn’t done so anyway (v. 14). He was so enraged because they reneged on the covenant they made right before Him, in His temple (v. 18) and thereby profaned His name (v. 16).
It is a solemn reminder to us of the warning in Ecclesiastes that “When you make a vow to God, do not delay to fulfill it. He has no pleasure in fools; fulfill your vow. It is better not to make a vow than to make one and not fulfill it. Do not let your mouth lead you into sin” (Eccl. 5:4-6a). God takes our vows seriously, especially the one that we make with our spouse before Him.