I Corinthians 9:13-15

Do you not know that those who minister the holy things eat of the things of the temple, and those who serve at the altar partake of the offerings of the altar? Even so the Lord has commanded that those who preach the gospel should live from the gospel. But I have used none of these things, nor have I written these things that it should be done so to me; for it would be better for me to die than that anyone should make my boasting void.