Numbers 31:19

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

Numbers 5:2

Command the children of Israel, that they put out of the camp every leper, and every one that hath an issue, and whoever is defiled by the dead:

Numbers 19:11-22

He that toucheth the dead body of any man shall be unclean seven days.

But the word of the LORD came to me, saying, Thou hast shed blood abundantly, and hast made great wars: thou shalt not build a house to my name, because thou hast 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.