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.”
Now therefore kill every male among the little ones, and kill every woman that hath known man by lying with him.
But all the women children, that have not known a man by lying with him, keep alive for yourselves.
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.
And purify all your raiment, and all that is made of skins, and all work of goats’ hair, and all things made of wood.
And Eleazar the priest said unto the men of war which went to the battle, This is the ordinance of the law which the Lord commanded Moses;
Counter-Arguments
The strongest case that this verse does not belong in this theme.

Related Verses
“And ye shall wash your clothes on the seventh day, and ye shall be clean, and afterward ye shall come into the camp.”
“He shall purify himself with it on the third day, and on the seventh day he shall be clean: but if he purify not himself the third day, then the seventh day he shall not be clean.”
“And the clean person shall sprinkle upon the unclean on the third day, and on the seventh day: and on the seventh day he shall purify himself, and wash his clothes, and bathe himself in water, and shall be clean at even.”
“He that toucheth the dead body of any man shall be unclean seven days.”
“And whosoever toucheth one that is slain with a sword in the open fields, or a dead body, or a bone of a man, or a grave, shall be unclean seven days.”