TSK
Treasury of Scripture Knowledge references in ASV.
And I, behold, I have taken the Levites from among the children of Israel instead of all the first-born that openeth the womb among the children of Israel; and the Levites shall be mine:
and Aaron shall offer the Levites before Jehovah for a wave-offering, on the behalf of the children of Israel, that it may be theirs to do the service of Jehovah.
the same shall purify himself therewith 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.