When it is said that God is unchanging, or immutable, it does not mean that He can change but simply does not. It means that He cannot change. God was the same when He created the earth as He is today. ... God is unchanging in His being, perfection, purposes, and promises.

Why is God immutable?

Nothing can gain or lose an essential property, for nothing can fail to have such a property. For Western theists, God is by nature a spirit, without body. If he is, God cannot change physically — he is physically immutable. So the Western God could at most change mentally- in knowledge, will, or affect.

What does the Bible say about God's Unchanging Hand?

Romans 8:35 "Hold On To God's Unchanging Hands."