2 Chronicles 29:15, 34

And they gathered their brethren, and sanctified themselves, and went in, according to the commandment of the king by the words of Jehovah, to cleanse the house of Jehovah.

But the priests were too few, so that they could not flay all the burnt-offerings: wherefore their brethren the Levites did help them, till the work was ended, and until the priests had sanctified themselves; for the Levites were more upright in heart to sanctify themselves than the priests.