There is no change in His being, in Himself. He always had the sovereign power to do whatever He wanted to do. The actual exercise of that in space and time is not a change in the being of God.
He was Creator before He created. He was Savior before He sent His Son. He was Rescuer before He brought anyone home to heaven. Those engagements of His qualities and attributes are not a change in His being, in Himself.
Ligonier Ministries