Exodus 19:10 King James Version (KJV)
10 And the Lord said unto Moses, Go unto the people, and sanctify them to day and to morrow, and let them wash their clothes,
Numbers 31:22-24 King James Version (KJV)
22 Only the gold, and the silver, the brass, the iron, the tin, and the lead,
23 Every thing that may abide the fire, ye shall make it go through the fire, and it shall be clean: nevertheless it shall be purified with the water of separation: and all that abideth not the fire ye shall make go through the water.
24 And ye shall wash your clothes on the seventh day, and ye shall be clean, and afterward ye shall come into the camp.