Leviticus 22:9
They shall therefore keep mine ordinance, lest they bear sin for it, and die therefore, if they profane it: I the LORD do sanctify them. They shall therefore keep mine ordinance, lest they bear sin for it, and die therefore, if they profane it: I the LORD do sanctify them.
The priests are commanded to keep the Lord's ordinance in their service before him. That keeping guards what is holy from being profaned through carelessness or disobedience. To profane holy things brings guilt upon the priests themselves, and that guilt brings death as its penalty. It is the Lord himself who sanctifies those who serve him in this careful obedience.