Deuteronomy 20:16. Thou shalt save alive nothing — No human creature; for the beasts, some few excepted, were given for a prey. This slaughter of all the people is to be understood only in case they did not surrender when summoned, but rejected the conditions of peace when offered them. In which case their condition was worse than that of any other people, whose males only were to be slain, Deuteronomy 20:14.

20:10-12 The Israelites are here directed about the nations on whom they made war. Let this show God's grace in dealing with sinners. He proclaims peace, and beseeches them to be reconciled. Let it also show us our duty in dealing with our brethren. Whoever are for war, we must be for peace. Of the cities given to Israel, none of their inhabitants must be left. Since it could not be expected that they should be cured of their idolatry, they would hurt Israel. These regulations are not the rules of our conduct, but Christ's law of love. The horrors of war must fill the feeling heart with anguish upon every recollection; and are proofs of the wickedness of man, the power of Satan, and the just vengeance of God, who thus scourges a guilty world. But how dreadful their case who are engaged in unequal conflict with their Maker, who will not submit to render him the easy tribute of worship and praise! Certain ruin awaits them. Let neither the number nor the power of the enemies of our souls dismay us; nor let even our own weakness cause us to tremble or to faint. The Lord will save us; but in this war let none engage whose hearts are fond of the world, or afraid of the cross and the conflict. Care is here taken that in besieging cities the fruit-trees should not be destroyed. God is a better friend to man than he is to himself; and God's law consults our interests and comforts; while our own appetites and passions, which we indulge, are enemies to our welfare. Many of the Divine precepts restrain us from destroying that which is for our life and food. The Jews understand this as forbidding all wilful waste upon any account whatsoever. Every creature of God is good; as nothing is to be refused, so nothing is to be abused. We may live to want what we carelessly waste.Forbearance, however, was not to be shown toward the Canaanite nations, which were to be utterly exterminated (compare Deuteronomy 7:1-4). The command did not apply to beasts as well as men (compare Joshua 11:11, Joshua 11:14).10-20. When thou comest nigh unto a city to fight against it, then proclaim peace unto it—An important principle is here introduced into the war law of Israel regarding the people they fought against and the cities they besieged. With "the cities of those people which God doth give thee" in Canaan, it was to be a war of utter extermination (De 20:17, 18). But when on a just occasion, they went against other nations, they were first to make a proclamation of peace, which if allowed by a surrender, the people would become dependent [De 20:11], and in the relation of tributaries the conquered nations would receive the highest blessings from alliance with the chosen people; they would be brought to the knowledge of Israel's God and of Israel's worship, as well as a participation of Israel's privileges. But if the besieged city refused to capitulate and be taken, a universal massacre was to be made of the males while the women and children were to be preserved and kindly treated (De 20:13, 14). By this means a provision was made for a friendly and useful connection being established between the captors and the captives; and Israel, even through her conquests, would prove a blessing to the nations. Heb. no seed, i.e. no man, as that word is oft used. Compare Joshua 10:40, with Deu 11:14. For the beasts, some few excepted as being under a special curse, were given them for a prey.

But of the cities of those people, which the Lord thy God doth give thee for an inheritance,.... The cities of the seven nations, six of which are mentioned by name in the next verse:

thou shalt save alive nothing that breatheth; the reason of this severity was because of their wickedness, the capital crimes and gross abominations they were guilty of, and for which they deserved to die; and on account whereof they were reserved to this destruction, when the measure of their iniquities was full, such as idolatry, incest, witchcraft, soothsaying, necromancy, &c. see Leviticus 18:3.

But of the cities of these people, which the LORD thy God doth give thee for an inheritance, thou shalt save alive nothing that breatheth: