“Every good gift and every perfect gift is from above, and comes down from the Father of lights, with whom there is no variation or shadow of turning”
with whom there is no variation
The light of God’s character and nature never changes. He is immutable.
“For I am the Lord, I do not change; Therefore you are not consumed, O sons of Jacob” (Malachi 3:6).”
Jesus Christ is the same yesterday, today, and forever” (Hebrews 13:8).
“This is the message which we have heard from Him and declare to you, that God is light and in Him is no darkness at all” (1 John 1:5).
or shadow of turning
The idea of a “turning” is a change, variation. God does not vary in His nature. There is no occasion where a shadow passes over God’s character. He has never had a single change in His character. We can render this phrase “a shade cast by change.” Shade changes with the movement of the sun and thus constantly changes. There is no mutation in God.
God does not change so we can count on Him to be consistent with Himself.
God does not change. He does not have the capability to change Himself much lest being changed by someone else. We can therefore count on Him. He is always true to Himself.