Numbers 31:19-21

Young's Literal Translation

¹⁹ `And ye, encamp ye at the outside of the camp seven days -- any who hath slain a person, and any who hath come against a pierced one, ye cleanse yourselves on the third day, and on the seventh day -- ye and your captives;

²⁰ and every garment, and every skin vessel, and every work of goats' [hair], and every wooden vessel, ye yourselves cleanse.'

²¹ And Eleazar the priest saith unto the men of the host who go in to battle, `This [is] the statute of the law which Jehovah hath commanded Moses: