Numbers 19:7-8, 21

After the priest has washed himself and his clothes with water, he may come back into the camp, but he will be unclean until evening. The man who burns the cow must wash himself and his clothes in water; he will be unclean until evening.

This is a lasting rule. Those who sprinkle the cleansing water must also wash their clothes, and anyone who touches the water will be unclean until evening.