Numbers 25:1 - Wesley's Explanatory Notes

Shittim — And this was their last station, from whence they passed immediately into Canaan. This is noted as a great aggravation of their sin, that they committed it, when God was going to put them into the possession of their long — expected land. The people — Many of them. Whoredom — Either because they prostituted themselves to them upon condition of worshipping their God: or because their filthy God was worshipped by such filthy acts, as Priapus and Venus were. The daughters of Moab — And of Midian too; for both these people being confederated in this wicked design, the one is put for the other, and the daughters of Moab may be named, either because they began the transgression, or because they were the chief persons, possibly, the relations or courtiers of Balak.