Numbers 19:15

‘Or a person who touches any unclean thing, whether a carcass of an unclean beast or the carcass of unclean cattle or a carcass of unclean swarming things—though it is hidden from him, yet he is unclean—will be guilty.

‘All the days of his dedication as a Nazirite to Yahweh he shall not go near to a dead person.

But there were some men who were unclean because of a dead person, so that they could not celebrate Passover on that day; so they came near before Moses and Aaron on that day.

“And you, camp outside the camp seven days; whoever has killed any person and whoever has touched any slain, purify yourselves, you and your captives, on the third day and on the seventh day.

“And after he is cleansed, seven days shall be counted for him.