1 Corinthians 9:
13 Do ye not know that they which minister about holy things live of the things of the temple? and they which wait at the altar are partakers with the altar?
14 Even so hath the Lord ordained that they which preach the gospel should live of the gospel.
15 But I have used none of these things: neither have I written these things, that it should be so done unto me: for it were better for me to die, than that any man should make my glorying void.
16 For though I preach the gospel, I have nothing to glory of: for necessity is laid upon me; yea, woe is unto me, if I preach not the gospel!
17 For if I do this thing willingly, I have a reward: but if against my will, a dispensation of the gospel is committed unto me.
18 What is my reward then? Verily that, when I preach the gospel, I may make the gospel of Christ without charge, that I abuse not my power in the gospel.
1 Cor. 9:13-18