And purify all your raiment, and all that is made of skins, and all work of goats' hair, and all things made of wood.

Wesley's Notes

31:20 Your raiment - Namely, your spoil and prey. All work - All which had contracted some ceremonial uncleanness either from the dead bodies which wore them, or the tents or houses where they were, in which such dead bodies lay, or from the touch of the Israelitish soldiers, who were legally defiled by the slaughters they made.

King James Translators' Notes

that...: Heb. instrument, or, vessel of skins

Matthew Henry's Concise Commentary

31:19-24 The Israelites had to purify themselves according to the law, and to abide without the camp seven days, though they had not contracted any moral guilt, the war being just and lawful, and commanded by God. Thus God would preserve in their minds a dread and detestation of shedding blood. The spoil had been used by Midianites, and being now come into the possession of Israelites, it was fit that it should be purified.

Matthew Henry's Whole Bible Commentary

Verses 13-24

We have here the triumphant return of the army of Israel from the war with Midian, and here,

I. They were met with great respect, v. 13. Moses himself, notwithstanding his age and gravity, walked out of the camp to congratulate them on their victory, and to grace the solemnity of their triumphs. Public successes should be publicly acknowledged, to the glory of God, and the encouragement of those that have jeoparded their lives in their country's cause.

II. They were severely reproved for saving the women alive. It is very probable that Moses had commanded them to kill the women, at least this was implied in the general order to avenge Israel of the Midianites; the execution having reference to that crime, their drawing them in to the worship of Peor, it was easy to conclude that the women, who were the principal criminals, must not be spared. What! says Moses, have you saved the women alive? v. 15. He was moved with a holy indignation at the sight of them. These were those that caused the children of Israel to commit this trespass; and therefore, 1. It is just that they should die. The law in case of whoredom was, The adulterer and adulteress should surely be put to death. God had put to death the adulterers of Israel by the plague, and now it was fit that the adulteresses of Midian, especially since they had been the tempters, should be put to death by the sword. 2. "It is dangerous to let them live; they will be still tempting the Israelites to uncleanness, and so your captives will be your conquerors and a second time your destroyers." Severe orders are therefore given that all the grown women should be slain in cold blood, and only the female children spared.

III. They were obliged to purify themselves, according to the ceremony of the law, and to abide without the camp seven days, till their purification was accomplished. For, 1. They had imbrued their hands in blood, by which though they had not contracted any moral guilt, the war being just and lawful, yet they were brought under a ceremonial uncleanness, which rendered them unfit to come near the tabernacle till they were purified. Thus God would preserve in their minds a dread and detestation of murder. David must not build the temple because he had been a man of war, and had shed blood, 1 Chr. 28:3. 2. They could not but have touched dead bodies, by which they were polluted, and that required they should be purified with the water of separation, v. 19, 20, 24.

IV. They must likewise purify the spoil they had taken, the captives (v. 19) and all the goods, v. 21-23. What would bear the fire must pass through the fire, and what would not must be washed with water. These things had been use by Midianites, and, having now come into the possession of Israelites, it was fit that they should be sanctified to the service of that holy nation and the honour of their holy God. To us now every thing is sanctified by the word and prayer, if we are sanctified by the Spirit, who is compared both to fire and water. To the pure all things are pure.