And the LORD spake unto Moses, saying,
The Lord spake unto Moses, saying, Avenge ... of the Midianites - a semi-nomadic people, descended from Abraham and Keturah, occupying a tract of country east and southeast of Moab, which lay on the eastern coast of the Dead Sea. They seem to have been the principal instigators of the infamous scheme of seduction planned to entrap the Israelites into the double crime of idolatry and licentiousness, by which it was hoped the Lord would withdraw from that people the benefit of His protection and favour.
Moreover, the Midianites had rendered themselves particularly obnoxious by entering into a hostile league with the Amorites (Joshua 13:21). The Moabites were at this time spared in consideration of Lot (Deuteronomy 2:9), and because the measure of their iniquities was not yet full. God spoke of avenging "the children of Israel;" Moses spoke of avenging the Lord, as dishonour had been done to God, and an injury inflicted on His people. The interests were identical. God and his people have the same cause, the same friends and assailants. This, in fact, was a religious war, undertaken by the express command of God against idolaters who had seduced the Israelites to practice their abominations.