God’s immutability. When I first heard of this attribute of God I thought that it meant that no one could shut God’s mouth, but I was a little off. Here is how we will define God’s immutability:
God is remains exactly the same in His nature and being eternity past, present and future. God not only does not change, He cannot change nor can He be changed by anyone or anything.
Let’s look at some Scripture to show where this doctrine come from.
"For I the LORD do not change; therefore you, O children of Jacob, are not consumed."
"25Of old you laid the foundation of the earth,and the heavens are the work of your hands. 26They will perish, but you will remain;they will all wear out like a garment. You will change them like a robe, and they will pass away, 27but you are the same, and your years have no end."
"God is not man, that he should lie, or a son of man, that he should change his mind. Has he said, and will he not do it? Or has he spoken, and will he not fulfill it?"
"Every good gift and every perfect gift is from above, coming down from the Father of lights with whom there is no variation or shadow due to change."
"Jesus Christ is the same yesterday and today and forever."
It is clear that Scripture teaches that God does not change, and indeed He cannot change because it would be contrary to His nature. We see above in Malachi 3:6 that it is said as clear as possible that "I the LORD do not change." Therefore should God change He would become a liar, and if He became a liar then He would become a sinner and cease to be God.
It’s a misnomer to say that God can do anything. More accurately we should say that God can do anything that is not counter to His nature. "God is not man, that He should lie." Lie is counter to God’s perfect and Holy nature therefore God is incapable of lying. So the age old question "Can God make a rock so big that He can’t pick it up?" is quite answerable. No, He cannot. God is omnipotent and has unlimited strength as well as unlimited creative powers. God could not create something that would deny His omnipotence, like a rock to big to pick up.
All that said, God’s immutability is very important. If God could say one thing and then change His mind, then the believer would have no security in the promises of God. God might decide not to save the one who places their faith in Jesus.
Furthermore, Scripture teaches that God is perfect. Therefore if God were to change He would not change for the better, there is no better than perfect. So by default if God were to change He would become imperfect. What kind of confidence could we have in an imperfect God? If God could change from being perfect in Holiness, and might, and such as these and become not holy, not almighty, what promise is there that we could be sure that He would or could keep. Perhaps in the end Satan would prevail over this changing God.
However this changeable God is not the God revealed in the Scriptures. The God of the Bible is a perfect God that cannot change or be changed. And we should thank Him daily for this part of His nature, for the security of the believer is found in this doctrine of God’s immutability.