Shadows are where things hidden lay or where those who wish to hide lurk. These are not characteristics of the Living God:
Do not be deceived, my beloved brothers. Every good gift and every perfect gift is from above, coming down from the Father of lights, with whom there is no variation or shadow due to change [or, turning.] Of his own will he brought us forth by the word of truth, that we should be a kind of firstfruits of his creatures. James 1:16-18 English Standard Version (ESV)
Do not err. This is an argument from what is opposite; for as God is the author of all good, it is absurd to suppose him to be the author of evil. To do good is what properly belongs to him, and [is] according to his nature; and from him all good things come to us.
…James, leaving to God his right and office of punishing, only removes blame from him. This passage teaches us, that we ought to be so affected by God’s innumerable blessings, which we daily receive from his hand, as to think of nothing but of his glory; and that we should abhor whatever comes to our mind, or is suggested by others, which is not compatible with his praise.
God is called the Father of lights, as possessing all excellency and the highest dignity. And when [James] immediately adds, that there is in him no shadow of turning, he continues the metaphor; so that we may not measure the brightness of God by the irradiation of the sun which appears to us.
Indeed, God’s glory is unlike that of the sun. The sun’s light causes a sundial’s shadow to process around a dial by which we may tell time. His radiance is unchanging; as it were, without shadow. Calvin goes on:
Of his own will. He now brings forward a special proof of the goodness of God which he had mentioned, even that he has regenerated us unto eternal life. This [is an] invaluable benefit [that] every one of the faithful feels in himself. [Therefore,] the goodness of God, when known by experience, ought to remove from [the regenerated] all contrary opinion respecting him.
…This passage teaches us, that as our election before the foundation of the world was [unmerited], so we are illuminated by the grace of God alone as to the knowledge of the truth, so that our calling corresponds with our election. The Scripture shows that we have been gratuitously adopted by God before we were born.
But James expresses here something more, that we obtain the right of adoption, because God…also calls us gratuitously (Ephesians 1:4, 5.) Farther, we…learn, that it is the [unique] office of God…to regenerate us [spiritually…]
That the same thing [(i.e., spiritual regeneration)] is sometimes ascribed to the ministers of the gospel, means [nothing] other…than this, that God acts through them; and it happens indeed through them, but he nevertheless alone does the work.
The word begotten means that we become new men, so that we put off our former nature when we are effectually called by God. He adds how God begets us, even by the word of truth, so that we may know that we cannot enter the kingdom of God by any other door.
And, finally, he says:
That we should be a kind of firstfruits of his creatures. The word τινὰ, “some,” has the meaning of likeness, as though he had said, that we are in a manner firstfruits. But this ought not to be restricted to a few of the faithful; but it belongs to all in common.
For as Man excels among all creatures, so the Lord elects some from the whole mass and separates them as a holy offering, to himself. It is no common nobility into which God extols his own children. Then justly are they said to be excellent as firstfruits, when God’s image is renewed in them.