The Spirit here refers back to the promise of Jeremiah 31:27-34. (And Jeremiah 33:1-9. Again, I can raise more questions than I can answer.) Jeremiah's promises were given to Hebrews who were in Babylonian captivity, and his promises looked forward to the freedom from Babylon and resettlement in Palestine, and to the premises in Christ Jesus.
Jeremiah 31:27-34 is quoted twice in the New Testament, showing us that this is a summary of the covenant of grace made with believers in Christ Jesus, Hebrews 8:8, 9 and Hebrews 10:1-18.
First, Jeremiah 31:27, prophecies that the day will come, and that day is the day of the Gospel Church, which is built upon the work and words of Jesus Christ. In that day, there will be a mighty increase in the seed of Abraham.
The promise is a reminder of the promise given to Abraham, Genesis 15:16. (Note the land promised to Abraham and his seed is the world, Romans 4:13.) The promised Seed was Christ, Galatians 3:16-29. And thus the covenant is made here in Jeremiah with the Gospel Church, Galatians 6:16, or the spiritual seed of believing Abraham.
Just as Judah and Israel, that had been two separate kingdoms, were united after their return from Babylon captivity, so were the Jews and Gentiles united in the Gospel Church under the new covenant.
Second, vv. 29, 30, the wicked were complaining against God, saying that because of their fathers' sins, they were now exiles born in Babylon. The promise is that the day is coming when the suffering for the fathers' sins in national captivity in Babylon will come to an end. Though the national captivity will end, they as individuals will not be free from the results of individual sin. In those daysthat is, the days of Christ. In other words, v. 29 prophecies of day that was to come in Christ when each person will be held responsible for his own sin.
V. 29, In those days they shall say no more implies that before Christ, the children paid a much higher price for the parents' sins than is common after Christ.
NOTE that sooner or latter the "sweetness" of sin will be turned into "sour grapes."
Noteit rains on the just and the unjust, so both the righteous and unrighteous must suffer the natural consequences for the sins of society. In other words, God promised to withhold rain in its season from the people who rebel against Him, Deuteronomy 28. He also promised tyrannical civil government against the people who reject His just government, Judges 8.
However, on individual level, we can enjoy God's blessings regardless of how our fathers acted, BECAUSE OF CHRIST. A promise of the new covenant is that His blood breaks the bondage of our parents' sins, 1 Peter 1:19.
Third, v. 32, this is a New covenant, which is clearly unlike the Old covenant given at the Mount. The New promised a new heart, an obvious reference to the new heart in conversion, Ezekiel 11:19, 36:26, 2 Corinthians 3:3.
Old vs. New
Certainly, under the Old covenant, people were saved by repentance and faith, same as under the New covenant. Under the Old, they had to look by faith to the Messiah to come, whose shed blood was typified in the required sacrifices. (Exodus 24:7, 8.)
But all of those things were only dark shadows and mysteries of what was to come in Christ. The New covenant contains primarily spiritual blessings, though we must not discount the physical blessings promised us in Christ. Under the New covenant, God writes His laws in the minds and hearts of His people, so that they willingly follow Him. Hebrews 8:9.
Under the Old covenant, God had to take His people by the hand, and lead them every step of the way, Jeremiah 31:32. Under the New, His people willingly follow Him.
Under the Old, God dwelt in a tent and latter in the temple. Under the New, God dwells in the temple made without handsin His people.
Under the Old, God the Father had to be worshiped in a central location. Under the New, God the Father is worshiped anywhere through the Spirit through Christ.
Under the Old, only a few knew and worshiped the Father, and that knowledge and worship was through the very restricted Hebrew manner of worship, and the proper worship could only be done in the land of Judah.
Under the New, the knowledge and worship of the Father is opened up to all men everywhere, as God calls them by His Sovereign Grace.
And the implication here is that UNDER THE OLD, individual children paid the price for the fathers' sins. But UNDER THE NEW, there can be a breaking of that hold of sin from father to son through the blood of Christ.
The basic difference between the Old and the New covenants is thisthough they were both grounded in Christ Jesus, the New has the person and blood of Christ and the abundant grace of the Holy Spirit as given to His Church under the gospel.
NOTE that God's laws are the same under both covenants, with the exception of the sacrifices that pointed to Christ. There is no hint that the law of the old covenant, the Ten Commandments, changed under the new covenant. Compare Jeremiah 31:33, I will put my laws in their inward parts... with Hebrews 8:10, I will put my laws into their mind... The same external law of the Old is not internal under the New.
Objection: Since Paul did not regive the Ten Commandments as given by Moses, then they no longer bind the believers. It is interesting that Paul reiterated several of the commandments in Romans 13:9, so those haters of Moses say that only the ones Paul reiterated are binding. However, Paul did not reiterate the one about honouring your parents, so I suppose that releaves them of that responsibility also.
A common arguement is also that since Paul did not restate the Sabbath law as given by Moses, that means that he voided the whole of Moses' law. Two points:
Romans 3:30 Seeing it is one God, which shall justify the circumcision by faith, and uncircumcision through faith. 31 Do we then make void the law through faith? God forbid: yea, we establish the law.
Second, Christ is our Sabbath, so that law is done away with, just as are the sacrificial laws.
Note the blinded minds and hearts under the old covenant, with the blinders removed under the new, 2 Corinthians 3:14.
Let me mention that Adam was created under a covenant of worksif he keep perfectly the command-word of God, he would be saved. He did not, so he moved from a covenant of works to a covenant of grace. That is to say, the faith given man by God's grace allows him to trust in the perfect work of the second Adam, Christ Jesus. And thus the fallen sons of Adam enter into His work for them, and he suffers the penalty of missing the mark (less than perfect work) for His people. (Isa. 53.) He fulfills the conditions of the covenant of works for us, and we are brought into His covenant by a work of the Holy Spirit. (Christ is the covenant, Isa. 42:6, 49:8.)
Fourth, v. 33, the promise is to give a new heart; the promise is not to give then a physical land. The promise is that He will be their God, and they will be His people, Hebrews 11:6, Revelation 21;3. And we are made His people by the grace of His power.
Fourth, v. 34, the promise is that in that day, He will remember their sin no more. The term remember their sins no more is only used three times in the Scripture, and all three deal with the New covenant in Christ. Hebrews 8:12, 10:17.
Because of Christ, God the Father is ready to comfort those who repent of and turn from their sins, v. 28. Because of Christ, He watches over His people for good, where before Christ, He watched over them, to pluck up, and to break down, and to throw down, and to destroy, and to afflict.
Fifth, Jeremiah 31:34 might be understood as the Spirit of God working from the inside to bring people to the knowledge of Christ, where under the Old, He worked from the outside and through others. However, we are clearly told that it is through the preaching of the gospel that the lost are brought to Christ. But salvation is of the Lord, so He must work from the inside:
John 6:45 It is written in the prophets, And they shall be
all taught of God. Every man therefore that hath heard, and hath
learned of the Father, cometh unto me.
1 Corinthians 2:10 But God hath revealed them unto us by his Spirit: for the Spirit searcheth all things, yea, the deep things of God.
1 John 2:20 ¶ But ye have an unction from the Holy One, and ye know all things.
Romans 11:33 O the depth of the riches both of the wisdom and knowledge of God! how unsearchable are his judgments, and his ways past finding out! 34 For who hath known the mind of the Lord? or who hath been his counsellor? 35 Or who hath first given to him, and it shall be recompensed unto him again? 36 For of him, and through him, and to him, are all things: to whom be glory for ever. Amen.
Concerning Eli: God did not change His mind concerning the curse. Does that mean that we must pay the price for our parents sin?
The weight of Scripture says that under the New covenant established by and in Christ, His blood frees us from the individual curse of the sins of our fathers, 1 Peter 1:19. However, on the national level, it is obvious that Deuteronomy 28 and 1 Samuel 8 are still very much in effect.
The basic difference between the old and the new covenant is the old was sealed with the blood of bulls and goats, and the new was sealed with the blood of Christ. The laws are still the same, but the ordinances and ceremonies that pointed to Christ are done.