Matthew Poole and continuators on Deuteronomy 32:5

5 They have corrupted themselves , their spot is not the spot of his children: they are a perverse and crooked generation .

(i. e.) The Israelites, as the following words manifest.

This phrase sometimes in Scripture notes sin, and sometimes destruction. And so the sense may be either 1. Their wickedness is not from God but from themselves, and their own choice, they have wilfully and industriously depraved themselves, and sold themselves to sin. Or rather 2. Their destruction is not from God, who is just and true, &c. as was now said, but wholly and solely from themselves, and from their own wickedness, as it here follows.

(i. e.) Their blemishes or sins are not committed through ignorance or frailty or surprizal, as good men sometimes sin, but they proceed from design and deliberation, are accompanied with malice and wilfulness and contempt, and followed with obstinacy, impenitency and incorrigibleness. So that they carry themselves not like my children and people as they seem to be and profess to be, but like mine enemies.

Not onely some few of them but the whole body or generation of them are perverse, (i. e.) froward and untractable, and crooked, (i. e.) irregular and disorderly, not agreeing with the straight and righteous nature of God and of his law. Compare Isa. 42. 16.

Marginal references: Heb. he hath corrupted to himself.; Or, that they are not his children that is their blot.