God is immutable, meaning he is unchanging and cannot be changed. This document provides three reasons for God's immutability:
1) God exists outside of time, and change can only occur over time. Since God created time, he is not subject to change.
2) For God to change, he would need to get better or worse, but as a perfect being he cannot improve, and cannot become imperfect by getting worse.
3) As an omniscient being, God knows all things already and cannot learn or gain new information. passages that describe God changing refer to external events, not God himself changing.