II Chronicles 29:15, 34

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

But the priests were too few, so that they could not skin all the burnt offerings; therefore their brethren the Levites helped them until the work was ended and until the other priests had sanctified themselves, for the Levites were more diligent in sanctifying themselves than the priests.