1 Corinthians 9:23 (KJV)

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.

For though I be free from all men, yet have I made myself servant unto all, that I might gain the more.

And unto the Jews I became as a Jew, that I might gain the Jews; to them that are under the law, as under the law, that I might gain them that are under the law;

To them that are without law, as without law, (being not without law to God, but under the law to Christ,) that I might gain them that are without law.

To the weak became I as weak, that I might gain the weak: I am made all things to all men, that I might by all means save some.

Know ye not that they which run in a race run all, but one receiveth the prize? So run, that ye may obtain.

And every man that striveth for the mastery is temperate in all things. Now they do it to obtain a corruptible crown; but we an incorruptible.

I therefore so run, not as uncertainly; so fight I, not as one that beateth the air:

But I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway.