God is a Spirit, infinite, eternal and unchangeable in his being, wisdom, power, holiness, justice, goodness and truth.
For I the Lord do not change; therefore you, O children of Jacob, are not consumed (Malachi 3:6).
God does not and cannot change.
I am constantly changing. I am not the same person I was yesterday. I become stronger, or weaker each day. I change in size. I learn things and I grow in understanding.
Because of this, you and I change our mind all the time. We discover new things that alter our view on truth. Our concept of right and wrong is constantly refined. Our eyes are at times opened to things that are sinful that we didn’t know about before. Or our hearts become hardened and we view things as evil that we previously thought were good.
Whenever I promise to do something, it is entirely possible that I won’t have the capability to deliver on that promise tomorrow. I might fall sick or have something urgent come up that changes my plans.
God is entirely unlike us in this.
He doesn’t change in His being – He is pure perfection and completion. For Him to change in His being He could only become less perfect. He cannot grow.
He doesn’t change His mind – He has perfect knowledge and knows the complete truth. He cannot learn and nothing ever surprises Him. Therefore, He doesn’t change His plans. He has only ever had one plan for history.
He doesn’t change His promises. Nothing can stop God from delivering on His promises and, because God is the ultimate sovereign cause of all things, nothing happens outside of His will.
God’s morality never changes. What God thinks is good has always been good and always will be good.
The Bible is full of passages emphasising this aspect of God. God is called a rock, and a strong tower. Multiple verses explicitly state that God doesn’t change.
James 1:17 says “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.”
Or in Malachi 3:6 we read “For I the Lord do not change; therefore you, O children of Jacob, are not consumed.”
This is the heart of this doctrine. God is utterly and completely reliable because He cannot and will not change.
– Tom Eglinton