Deuteronomy 21:10-14 -

If an Israelite saw among captives taken in war a woman, fair of aspect, and loved her, and took her to be his wife, he was to allow her a full month to mourn her lost kindred, and become accustomed to her new condition, before he consummated his union with her. This refers to captives from other nations than those of Canaan, with whom the Israelites were to form no alliance, and whom they were not to take captive, but either wholly destroy or render tributary (cf. Deuteronomy 7:3 ; Numbers 21:1 , etc.; Joshua 11:19 ).