Moses
Numbers 25:3ESV·traditional attribution

So Israel yoked himself to Baal of Peor. And the anger of the LORD was kindled against Israel.

John Calvin Reformed @genevareformer

3. AndIsrael joined himself to Baal-peor. Moses amplifies their crime by this expression, that they bound themselves to the idol in an impious alliance; and thus he alludes to that holy union whereby God had connected Himself with the people, and accuses them of broken faith and wicked rebellion.

Matthew Henry Presbyterian @wholebiblehenry

Here is, I. The sin of Israel, to which they were enticed by the daughters of Moab and Midian; they were guilty both of corporal and spiritual whoredoms, for Israel joined himself unto Baal-peor, Num 25:3. Not all, nor the most, but very many, were taken in this snare. Now concerning this observe, 1.

Commenting on Numbers 25:1-5

John Gill Reformed Baptist @doctorgill

And Israel joined himself unto Baalpeor,.... The name of an idol; one of the Baals, Baal being a general name for an idol; and, to distinguish this from other Baals or idols, it was called Peor, either from its opening its mouth in prophecy, as Ainsworth; or from some obscene posture and action used in the worship of it, being, as it is by many...