TSK
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"Behold, I have taken the Levites from among the children of Israel instead of all the firstborn who open the womb among the children of Israel; and the Levites shall be mine:
and Aaron shall offer the Levites before Yahweh for a wave offering, on the behalf of the children of Israel, that it may be theirs to do the service of Yahweh.
the same shall purify himself with water on the third day, and on the seventh day he shall be clean: but if he doesn't purify himself the third day, then the seventh day he shall not be clean.