Moses
Deuteronomy 32:17ESV·traditional attribution

They sacrificed to demons that were not God, to gods they had never known, to new gods that had come recently, whom your fathers had never dreaded.

Matthew Henry Presbyterian @wholebiblehenry

We have here a description of the apostasy of Israel from God, which would shortly come to pass, and to which already they had a disposition. One would have thought that a people under so many obligations to their God, in duty, gratitude, and interest, would never have turned from him; but, alas! they turned aside quickly.

Commenting on Deuteronomy 32:15-18

John Gill Reformed Baptist @doctorgill

Of the rock that begat thee thou art unmindful,.... The same with the rock of salvation, Deu 32:15; repeated and expressed in different words, that their wretched ingratitude might be taken notice of and observed: begetting is ascribed to this rock, as regeneration is to Christ, Jo1 2:29; and was true of some among the Jews: some choose to render the words, "the rock of...

Jamieson-Fausset-Brown Reformed @jfbcommentary

They sacrificed unto devils--(See on Lev 17:7).