The immutability of God (His quality of not changing) is clearly taught throughout Scripture. For example, in Malachi 3:6 God affirms, "I the Lord do not change." (See also Numbers 23:19; 1 Samuel 15:29; Isaiah 46:9-11; and Ezekiel 24:14.)
James 1:17 also teaches the immutability of God: “Every good gift and every perfect gift is from above and comes down from the Father of lights, with whom is no variableness nor shadow of turning.” The “shadow of turning” refers to our perspective on the sun: it is eclipsed it moves and it casts its shadow. The sun rises and sets, appears and disappears every day; it comes out of one tropic and enters into another at certain seasons of the year. But with God, who, spiritually speaking, is light itself, there is no darkness at all; there is no change with Him, nor anything like it. God is unchangeable in His nature, perfections, purposes, promises, and gifts. He, being holy, cannot turn to that which is evil; nor can He, who is the fountain of light, be the cause of darkness. Since every good and perfect gift comes from Him, evil cannot proceed from Him, nor can He tempt any to it (James 1:13). The Bible is clear that God does not change His mind, His will, or His nature.
There are several logical reasons why God must be immutable, that is, why it is impossible for God to change. First, if anything changes, it must do so in some chronological order. There must be a point in time before the change and a point in time after the change. Therefore, for change to take place it must happen within the constraints of time; however, God is eternal and exists outside of the constraints of time (Psalm 33:11; 41:13; 90:2-4; John 17:5; 2 Timothy 1:9).
Second, the immutability of God is necessary for His perfection. If anything changes, it must change for the better or the worse, because a change that makes no difference is not a change. For change to take place, either something that is needed is added, which is a change for the better; or something that is needed is lost, which is a change for the worse. But, since God is perfect, He does not need anything. Therefore, He cannot change for the better. If God were to lose something, He would no longer be perfect; therefore, He cannot change for the worse.
Third, the immutability of God is related to His omniscience. When someone changes his/her mind, it is often because new information has come to light that was not previously known or because the circumstances have changed and require a different attitude or action. Because God is omniscient, He cannot learn something new that He did not already know. So, when the Bible speaks of God changing His mind, it must be understood that the circumstance or situation has changed, not God. When Exodus 32:14 and 1 Samuel 15:11-29 speak of God changing His mind, it is simply describing a change of dispensation and outward dealings toward man.
Numbers 23:19 clearly presents the immutability of God: “God is not a man, that He should lie, nor a son of man, that He should change His mind. Does He speak and then not act? Does He promise and not fulfill?” No, God does not change His mind. These verses affirm the doctrine of God’s immutability: He is unchanging and unchangeable.