Jeremiah 31:33

Instead of God’s law being external to them, the Lord would write it on their heart (i.e., mind and will; cf. Jeremiah 17:1). He will do something for them that they cannot do for themselves (cf. Deuteronomy 30:5-6). "Writing on the heart" suggests the removal of written documents and merely human mediators. Having the Lord’s Word in the heart prevents sin and fosters obedience (cf. Deuteronomy 11:18; Psalms 119:11). [Note: See Femi Adeyemi, "What Is the New Covenant ’Law’ in Jeremiah 31:33?" Bibliotheca Sacra 163:651 (July-September 2006):312-21, who concluded that this refers not to the Mosaic Law but to a law yet to be given to Israel by Christ. Ibid., "The New Covenant Law and the Law of Christ," Bibliotheca Sacra 163:652 (October-December 2006):438-52, equated this new law with the Law of Christ (1 Corinthians 9:21; Galatians 6:2).] David equated having the law written on his heart with desiring to do God’s will (Psalms 40:8)

"It will become part of the nature of God’s people; it will be instinctive. The core of the new covenant is God’s gift of a new heart (cf. Ezekiel 36:25-27). Herein lies the sufficient motivation for obeying God’s law." [Note: Feinberg, "Jeremiah," p. 576. Italics mine. Cf. 32:39 [LXX]; Ezekiel 11:19; 18:31; and Wiersbe, p. 123.]

". . . there is no further need of any external means like mutual teaching about God . . ." [Note: Keil, 2:36.]

God would also enter into an intimate relationship with His people as His covenant partners (cf. Jeremiah 7:23; Jeremiah 11:4; Jeremiah 24:7; Jeremiah 30:22; Jeremiah 31:1; Jeremiah 32:38; Deuteronomy 31; Ezekiel 11:20; Ezekiel 36:28). The old Mosaic Covenant being broken, a new relationship would begin.

"If the sheer grace of God’s election of Israel as covenant partner was apparent in the first covenant making, how much more so in this promise following their history of unfaithfulness and rebellion (Jeremiah 31:32)." [Note: Scalise, p. 133.]

Notice that Jeremiah revealed nothing about human responsibility under the New Covenant. That would come later with the teachings of Jesus Christ and the apostles.