John Calvin Commentary Deuteronomy 32:5

"They have dealt corruptly with him, [they are] not his children, [it is] their blemish; [They are] a perverse and crooked generation." — Deuteronomy 32:5 (ASV)

They have corrupted themselves. Moses now unhesitatingly denounces the treachery of the people and unleashes the strongest rebukes. For if God is just and true, then it was clear enough that the Israelites were a depraved and perverse nation.

This perverse nation, he says, has corrupted itself in relation to Him—namely, the One whom he has just praised for His perfect justice and faithfulness. He accuses them of having basely prostituted to every kind of sin the purity they had pledged to God.

Undoubtedly, they were deeply hurt by these descriptions and would have been overcome with rage, if they had not seen that God’s incomparable servant, now called to die by God’s command, spoke as if from heaven. The voice of the dying man, therefore, restrained their pride, so that they did not dare to oppose him then as a mere mortal. Afterwards, when the condemnation had been approved by public authority and by common agreement, they were less free to unleash their fury against it.

He preemptively states that they were not His children, because otherwise they might obviously have objected that the sacred descendants of Abraham, whom God had adopted, should be treated less harshly. Moses, therefore, declares that they are not children because they are a perverse nation. For although their adoption always stood firm, its effectiveness was still restricted to the elect among them, so that God, without breaking His covenant, could reject the people as a whole.

But to explain this more clearly, we must remember that the Spirit, for different reasons, sometimes calls hypocrites God’s children and at other times denies them this name. For sometimes it makes their guilt worse when they are called children of Abraham and Jacob, as well as of God—an example of which will soon occur. Here, however, so that they might stop boasting without reason, they are said not to be children because they are degenerate and therefore disinherited by God, no longer retaining their honorable position. In this sense, Moses declares that they are not children, as they have rejected God as their Father.

It is added that this was “their spot” (or disgrace; ²⁵³), unless one prefers to understand that they were corrupted by their “spots,” or by their sins—an interpretation I willingly accept. However, I do not reject the other meaning: that their alienation from God had made them shameful, or that they had contracted the stain of disgrace through their faithlessness.

²⁵³ Added from the Fr..