Numbers 25:17 - Ellicott's Commentary On The Whole Bible

Vex the Midianites, and smite them. — The Midianites appear to have been joint actors with the Moabites throughout the whole of the opposition which was offered to Israel, and the chief actors in the wiles by which the Israelites were seduced. As the descendants of Abraham, the father of the faithful, the Midianites ought to have feared and obeyed Abraham’s God, and to have shown brotherly kindness to His people, who were their own kindred. The special judgments of God are directed against the sins of apostacy and of seduction. (Comp. Revelation 2:14; Revelation 18:6.) Although the Moabites were not to be smitten with the Midianites (see Deuteronomy 2:9), nevertheless they did not escape punishment, but were shut out, even to the tenth generation, from the congregation of the Lord. (See Deuteronomy 23:3-4.) Their exemption at this time from the judgment executed upon the Midianites was probably due, not to their descent from Lot (for the Midianites were descended from Abraham), but to the fact that the measure of their sin was not yet full. (Comp. Genesis 15:16.)