Leviticus 21:6 - Matthew Poole's English Annotations on the Holy Bible

Holy unto their God; devoted to God's service, and always prepared and fit for it; and therefore shall keep themselves as far as they can from all defilement, which makes them unmeet for their Master's use. Not profane the name of their God, which they especially bear; they shall not disparage the service of God by making it give place to such slight occasions. The bread of their God, i.e. the shew-bread; or rather, all the other offerings besides burntofferings; which are called bread, either because bread is commonly put for all food, as below, Leviticus 21:17,21; or because God is satisfied and refreshed with these offerings, as a man is with his bread; or rather, because they, or part of them, are the bread or food of the priests, and are here called the bread of their God, either objectively, because they were offered to God, or efficiently, because they were given by God to the priests. And these are called bread in opposition to the burnt-offerings, which being wholly consumed gave no food to the priests. Or, the offerings made by fire are here put synecdochically for all the rest, the most eminent kind for all, which are here called bread, because devoured by fire to the honour of God; for the particle and is not in the Hebrew, and may be omitted.