Keep alive for yourselves. — The Israelites were allowed to make slaves of their captives. Shortly after the capture of these Midianitish women, and, it may be, as arising out of it, the law concerning marriage with captives was enacted. (See Deuteronomy 21:10-14.)
Related Commentaries of Numbers 31:18
Numbers 31:18
18 But all the women children, that have not known a man by lying with him, keep alive for yourselves.