Numbers 31:19

And encamp ye without the camp seven days: every one killing a soul, and every one touching upon the wounded, ye shall be purified in the third day, and in the seventh day, ye and your captivity.

Numbers 5:2

Command the sons of Israel, and they shall send forth from the camp every one leprous, and every one flowing, and every one unclean for the soul:

Numbers 19:11-22

He touching upon the dead of any soul of man and he was unclean seven days.

And the word of Jehovah will be upon me, saying, Thou didst pour out blood for abundance, and didst make great wars: thou shalt not build a house for my name, for thou didst pour out many bloods in the earth before me.

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.