Números 31:19

19 "Anyone who has killed someone or touched someone who was killed must stay outside the camp seven days. On the third and seventh days you must purify yourselves and your captives.

19 And encamp ye without the camp seven days: whosoever hath killed any person, and whosoever hath touched any slain, purify yourselves on the third day and on the seventh day, ye and your captives.