Numbers 19:7, 8, 19

After that, the priest must wash his clothes and bathe himself with water. He may then come into the camp, but he will be ceremonially unclean till evening.

The man who burns it must also wash his clothes and bathe with water, and he too will be unclean till evening.

The man who is clean is to sprinkle those who are unclean on the third and seventh days, and on the seventh day he is to purify them. Those who are being cleansed must wash their clothes and bathe with water, and that evening they will be clean.