2 Chronicles 29:15, 34

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

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 other priests had sanctified themselves: for the Levites were more upright in heart to sanctify themselves than the priests.