1 Corinthians 9:24 (KJV)

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.

And this I do for the gospel's sake, that I might be partaker thereof with you.

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.