Immutability. That is one of the attributes, or characteristics, of God. A mutation is a change; to be mutable is to be able to change; to be immutable is to be changeless. God is immutable. But this is not just an empty idea. It provides great comfort to the people of God. In Malachi 3:6, God states, "For I am the LORD, I change not; therefore ye sons of Jacob are not consumed."
Notice the cause and effect of the passage. Because God changes not, the sons of Jacob are not consumed. Evidently, if God were changeable, He could take back His promises. And, if He took back His promises, He would have no reason to preserve His people when they were disobedient to Him. This truth is not just for Israel. I, too, am thankful that I serve a God who does not change. Otherwise, I am sure that I would have been consumed on certain occasions of disobedience and rebellion. What a wonderful God we serve!