Leviticus 22:7

And when the sun is down he shall be clean
Having washed himself in water, otherwise not, though the sun may be set: and shall afterwards eat of the holy things;
the families of the priests lived upon: because it [is] his food:
his common food, his ordinary diet, that by which he subsists, having nothing else to live upon; this being the ordination of God, that he which ministered about holy things should live on them; and these being his only substance, in compassion to him they were detained from him no longer than the evening; and this was done, to make him careful how he defiled himself, since thereby he was debarred of his ordinary meals.