Numbers 19:10-12

10The man who gathers up the ashes of the heifer must also wash his clothes, and he will remain ceremonially unclean until evening. This is a permanent law for the people of Israel and any foreigners who live among them.

11“All those who touch a dead human body will be ceremonially unclean for seven days.

12They must purify themselves on the third and seventh days with the water of purification; then they will be purified. But if they do not do this on the third and seventh days, they will continue to be unclean even after the seventh day.