Matthew Poole and continuators on Leviticus 21:1

1 AND the LORD said unto Moses, Speak unto the priests, the sons of Aaron, and say unto them, There shall none be defiled for the dead among his people:

To wit, by touching of the dead body, or abiding in the same house with it, or assisting at his funerals, or eating 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, Num. 6. 6. and 19. 11, 14, 16. Deut. 26. 14. Hos. 9. 4. And God would hereby teach them, and in them all successive Ministers of holy things, that they ought so entirely to give themselves to the service of God that they ought to renounce all expressions of natural affections, and all worldly employments so far as they are impediments to the discharge of their holy services. See Lev. 10. 3, 7. Deut. 33. 9. Mat. 8. 22. Hereby also God would beget in the people a greater reverence to the Priestly function, and oblige the Priests to a greater degree of strictness and purity than other men.

Marginal references: Ezek. 44. 25.