Verse 19. - Do ye abide without the camp. In this case at any rate the law of לִמְסָר־מַעַל 19:11 sq. was to be strictly enforced. And your captives, i.e., the women and children who were spared. No peculiar rites are here prescribed for the reception of these children of idolaters into the holy nation with which they were to be incorporated beyond the usual lustration with the water of separation. In after times they would have been baptized.

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.And do ye abide without the camp seven days..... Which was the time that anyone that touched a dead body remained unclean, Numbers 19:11,

whosoever hath killed any person; as most of them if not all must have done; all the males of Midian that fell into their hands being slain by them, that were men grown:

and whosoever hath touched any slain; as they must to strip them of their garments, and take their spoil from them:

purify both yourselves and your captives, on the third and on the seventh day; which were the days appointed for the purification of such that were polluted by touching dead bodies, Numbers 19:11 and their captives, which were the female little ones; (for as for the women, and males among the little ones, they were ordered to be slain;) though they were Heathens, yet inasmuch as they were to be for the service of the Israelites, and to be brought up in their religion, they were to be purified also; to which purpose is the note of Jarchi;"not that the Gentiles receive uncleanness and need sprinkling, but as ye are the children of the covenant, so your captives, when they come into the covenant, and are defiled, need sprinkling.''