Deuteronomy 32:17

Unto devils, i.e. unto idols, which the devils brought into the world in opposition to God, in and by which the devils ofttimes manifested themselves unto men, and gave them answers, and received their worship. Compare 1 Corinthians 10:20. The Gentiles pretended to worship God in those idols, and the devils which inspired them deluded the nations with false pretences that they were a sort of lower gods. Moses therefore takes off this mask, and shows the Israelites that these pretended gods were really devils, those great enemies of mankind, and therefore that it was the height of madness to honour or worship them. Not to God: this he saith, either because though at first they joined God and idols together in worship, yet at last they quite forsook God, and adhered to idols only; or because God utterly rejected those sacrifices which they offered to him together with idols, and took them for no sacrifices. See 1 Corinthians 10:21. Whom they knew not, or, who never knew them, i.e. never showed any kindness to them, or did them any good; for so words of knowledge are oft used, as Psalms 1:6 Hosea 13:5. That came newly up; not simply or absolutely, for some of these gods had been worshipped for many generations, and had a fair pretence of long antiquity, but comparatively to the true God, who is the Ancient of days, Daniel 7:9, and who was worshipped from the beginning of the world. To this original and first antiquity Moses recalls them; as also our Saviour doth recall the Jews to the first institution, Matthew 19:8. And therefore we may safely follow both their patterns in despising all pretences of antiquity, which are contrary to God's first institutions contained (as all confess) in the Holy Scriptures. Whom your fathers feared not, i.e. served not, worshipped not, but justly despised and abhorred them.