Numbers 31:19

"Encamp outside of the camp seven days: whoever has killed any person, and whoever has touched any slain, purify yourselves on the third day and on the seventh day, you and your captives.

Numbers 5:2

"Command the children of Israel that they put out of the camp every leper, and everyone who has an issue, and whoever is unclean by the dead.

Numbers 19:11-22

"He who touches the dead body of any man shall be unclean seven days:

But the word of Yahweh came to me, saying, 'You have shed blood abundantly, and have made great wars. You shall not build a house to my name, because you have shed much blood on the earth in my sight.

Treasury of Scripture Knowledge

Summary

Numbers 31:19

And do ye abide without the camp seven days: whosoever hath killed any person, and whosoever hath touched any slain, purify both yourselves and your captives on the third day, and on the seventh day.