“way.” The Hebrew word is literally “road,” and “road” was used idiomatically for a way of life, and the verse could be amplified somewhat to read, “And I will give them one heart and one way of life.” We see “road” used of a way of life in dozens of verses (cp. Ps. 1:1, 6; 18:30; 25:9; 37:5; 101:2; Prov. 2:20; 4:14, 19; 8:13; 11:20; 12:15; 13:6; 15:9, 19; 16:7; etc.).
Under the New Covenant, when people get a new heart and God puts His Word in people’s minds, people will live a godly life. They will all have one heart, and one godly way of life. The New Covenant, which was future to Jeremiah, has now been ratified with Christ’s blood and death on the cross. However, the covenant promises, such as these in Jeremiah 32:39, will not be fully realized until the Millennial Kingdom and First Resurrection, when Christ rules as king over the earth and the righteous believers are raised from the dead in their new everlasting bodies. It is common with covenants that there is a period of time—sometimes a long time—between when a covenant is ratified and when the covenant promises are fulfilled. For example, God made a blood covenant with Abraham and promised that Abraham and his offspring would get the Promised Land. It has now been 4,000 years and that covenant promise has not been fulfilled, but it will be. Part of the reason that believers of all time have a secure hope for the future is that God is a God who keeps promises.
[For more on the New Covenant, see commentary on Jeremiah 31:31. For more on Christ’s reigning as king on earth, see Appendix 3, “Christ’s Future Kingdom on Earth.” For more on the Rapture and resurrections, see commentary on Acts 24:15].
“forever.” This is expressed in the Hebrew text by the idiom, more literally translated as “all the days,” In this context this idiom means “forever” or “always.” This is a wonderful promise because it is saying that when God gathers Israel again, which will happen in the time of the New Covenant that people will get a new heart (they will all have “one heart”) and “a new spirit” (cp. parallel verse; Ezek. 11:19), and they will always fear God for their own good and for the good of their children. This promise is similar to the promise to the Christian Church that the New Birth is permanent (see commentary on 1 Peter 1:3).