Leviticus 22:7

And when the sun is down, he shall be clean, and shall afterward eat of the holy things; because it is his food.

Cross-references

Leviticus 21:22 similarly affirms that priests may eat holy bread—reinforcing that holy things are their food.

Numbers 18:11-19 specifies the priests' portions of offerings—the very 'holy things' they are entitled to eat.