The first covenant document was written by God on tablets of stone and was deposited in the ark of the covenant as an important witness of God’s covenant with His people (Exod. 31:18; Deut. 10:1–4). Documents written in stone, however, could be broken; and scrolls, as Jeremiah had experienced, could be cut up and burned (Jer. 36:23).

But in the new covenant God now will write His law in the hearts of the people. The heart refers to the mind, the organ of memory and understanding (Jer. 3:15; Deut. 29:4), and especially to where conscious decisions are made (Jer. 3:10; 29:13).

This promise did not simply secure access to and knowledge of the law by everyone. It also, and more importantly, was to bring about a change in the heart of the nation. The problem of Israel was that their sin was engraved “with a pen of iron,” “with the point of a diamond . . . on the tablet of their heart” (Jer. 17:1, NKJV). They had a stubborn heart (Jer. 13:10; 23:17); therefore, it was impossible for them to do the right thing (Jer. 13:23).

Jeremiah did not announce a change of the law, because the problem of Israel was not the law but the heart. God wanted Israel’s faithfulness to be a grateful response to what He had done for them; thus, He gave the Ten Commandments to them with a historical prologue, expressing His love and care for them (Exod. 20:1, 2). God wanted Israel to obey His laws as an acknowledgment that He wanted the best for them, a truth revealed in their great deliverance from Egypt. Their obedience was to be an expression of gratitude, a manifestation of the reality of their relationship.

The same is true today for us. Jesus’ love and care in dying for us is the prologue of the new covenant (Luke 22:20). True obedience comes from the heart as an expression of love (Matt. 22:34–40). This love is the distinguishing mark of the presence of the Holy Spirit in the life of the believer. God pours His love on us through His Spirit (Rom. 5:5), which is expressed in love (Gal. 5:22).