Malachi 3:6

The Lord concluded by reminding His people of one of His character qualities that should have made them fear Him and have hope. He does not change, and that is why they would not be consumed totally. He was faithful to His covenant promises in the Abrahamic and Mosaic Covenants; He would never destroy them completely but would chasten them and finally bless them. By calling the Jews "sons of Jacob," the Lord was connecting their behavior with that of their notorious patriarch. Promises are only as good as the person who makes them, so the fact that Yahweh does not change strengthens the certainty of their fulfillment (cf. Deuteronomy 4:31; Ezekiel 36:22-32). The Apostle Paul gave the same reason for expecting Israel to have a future (Romans 3:3-4; Romans 9:6; Romans 11:1-5; Romans 11:25-29).

The statement that Yahweh does not change (cf. 1 Samuel 15:29; Hebrews 13:8) may seem to contradict other statements that the Lord changed His mind (e.g., Exodus 32:14). This statement that He does not change refers to the essential character of God. He is always holy, loving, just, faithful, gracious, merciful, etc. The other statements, that He changes, refer to His changing from one course of action to another. They involve His choices, not His character. If He did not change His choices, He would be unresponsive; if He changed His character, He would be unreliable. [Note: See Thomas L. Constable, Talking to God: What the Bible Teaches about Prayer, pp. 145-46; Robert B. Chisholm Jr., "Does God ’Change His Mind’?" Bibliotheca Sacra 152:608 (October-December 1995):387-99; and Clendenen, pp. 404-8.]