Numbers 31:23-25

Young's Literal Translation

²³ every thing which may go into fire, ye cause to pass over through fire, and it hath been clean; only, with the water of separation it is cleansed, and all that may not go into fire, ye cause to pass over through water;

²⁴ and ye have washed your garments on the seventh day, and have been clean, and afterwards ye come in unto the camp.'

²⁵ And Jehovah speaketh unto Moses, saying,