Verse 2. - Avenge the children of Israel of the Midianites. The war was to be distinctly one of vengeance on the part of Israel. On the grave moral question which arises out of this war, and of the manner in which it was carried on, see the note at the end of the chapter. Afterward shalt thou be gathered unto thy people. It is quite possible that Moses himself had been reluctant to order the expedition against Midian, either because it involved so much bloodshed, or, more probably, because he foresaw the difficulty which actually arose about the women of Midian. If so, he was here reminded that his place was to obey, and that his work on earth was not done so long as the Midianites remained unpunished.

31:1-6 All who, without commission from God, dare to execute private revenge, and who, from ambition, covetousness, or resentment, wage war and desolate kingdoms, must one day answer for it. But if God, instead of sending an earthquake, a pestilence, or a famine, be pleased to authorize and command any people to avenge his cause, such a commission surely is just and right. The Israelites could show such a commission, though no persons now can do so. Their wars were begun and carried on expressly by Divine direction, and they were enabled to conquer by miracles. Unless it can be proved that the wicked Canaanites did not deserve their doom, objectors only prove their dislike to God, and their love to his enemies. Man makes light of the evil of sin, but God abhors it. This explains the terrible executions of the nations which had filled the measure of their sins.Avenge the children of Israel of the Midianites,.... For the injury they had done them, by sending their daughters among them, who enticed them to commit uncleanness with them, and then drew them into the worship of their idols, which brought the wrath of God upon them, and for which 24,000 persons were slain. Now, though the Moabites had a concern in this affair as well as the Midianites, yet they were spared; which some think was for the sake of Lot, from whom they descended; but why not the Midianites for the sake of Abraham, whose offspring they were by Keturah? Jarchi says, they were spared because of Ruth, who was to spring from them; and so she might, and yet vengeance be taken on great numbers of them: but the truer reason seems to be, either because the sin of the Moabites was not yet full, and they were reserved for a later punishment; or rather because they were not the principal actors in the above affair; but the Midianites, who seem to have advised Balak at first to send for Balaam to curse Israel, and who harboured that soothsayer after he had been dismissed by Balak, and to whom he gave his wicked counsel, and which they readily followed, and industriously pursued:

afterward shalt thou be gathered unto thy people; or die, see Numbers 27:13, it being some satisfaction to him to see the good land, as he did from Abarim, and the Israelites avenged on their enemies before his death.