Numbers 19:9-10

9Then a man who is clean must pick up all the ashes of the cow. And he must put them outside the camp in a clean place. Keep them safe there for all the Israelites. You must mix them with water to make special water. It will be water for someone who is not clean to make them holy again. It is water to remove sin.

10The man who picks up the ashes must also wash his clothes. He will not be clean until evening. This rule is for the Israelites and for all the people who are living with them.