How do we know God is immutable and cannot change?

The immutability of God is a crucial doctrine in Reformed theology, which holds that God, in His essence and attributes, cannot change. Malachi 3:6 states, 'For I am the Lord, I change not.' This unchanging nature assures believers of the reliability of God's promises and His eternal purposes. If God could change, He would not be God; the assurance found in His word would be rendered meaningless. His unchangeable love, justice, and truth show the consistency and faithfulness of His character throughout all ages.