Some consider the God of the Old Testament to be a God of anger and wrath and the God of the New Testament to be a God of grace and mercy. They think of God as constantly growing and changing.
They fail to consider that God, before any of the world was even created, already knew what he would do to offer saving grace to mankind. He had already determined that those in Christ would be His chosen ones and adopted children (Ephesians 1:3-5).
So much of what God does in the Old Testament is preparing man for the receiving of His great gift of grace. The Old Testament was intended to bring us to Christ, God’s great gift to us.
This idea of a changing God can lead to many misunderstandings.
Jesus Christ is the same yesterday and today and forever. (Heb 13:8)
The writer of Hebrews reminds us of the sameness of God and Jesus in the context of a warning to not be carried away by all kinds of strange teachings.
Stay with Jesus and what He has said. Do not allow the thoughts and ideas of men to move you away from Jesus and what He has said. The very words He has spoken will be the same words that will judge us in the last day.
Jesus is not changing. His word and will are not continually developing. It has been once and for all delivered to us. It is the same as it was and as it will be.