Numbers 31:19

And encamp ye outside 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, ye and your captives.

Numbers 5:2

Command the sons of Israel, that they put out of the camp every leper, and every man who has an issue, and whoever is unclean about life.

Numbers 19:11-22

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

But the word of LORD came to me, saying, Thou have shed blood abundantly, and have made great wars. Thou shall not build a house to my name because thou have shed much blood upon 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.