Leviticus 21:1

Among his people — None of the priests shall touch the dead body, or assist at his funeral, or eat of the funeral feast. The reason of this law is evident, because by such pollution they were excluded from converse with men, to whom by their function they were to be serviceable upon all occasions, and from the handling of holy things. And God would hereby teach them, and in them all successive ministers, that they ought entirely to give themselves to the service of God. Yea, to renounce all expressions of natural affection, and all worldly employments, so far as they are impediments to the discharge of their holy services.