V. Rom 1:23 and changed the glory of the incorruptible (αφθαρτου) God into an image made like corruptible man—and birds and four-footed animals and creeping things.
The term incorruptible does not mean immutable. The word aphthartou (αφθαρτου) is used in Corinthians to denote deterioration from good habits.
1 Corinthians 15:33
Do not be deceived: “Evil company corrupts good habits.”
Or the word could be used of our incorruptible bodies, implying a physical change, we receive at the coming of the Lord.
in a moment, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, and the dead will be raised incorruptible, and we shall be changed.
What incorruptible does not mean is that God is immutable in the classical definition of immutable. Certainly, when we receive our incorruptible bodies, our knowledge and power will not be equal to God’s.
God is absolutely immutable in his essence and attributes. He can neither increase nor decrease.
He is subject to no process of development, or of self-evolution. His knowledge and power can never be greater or less. Charles Hodge, Systematic Theology