'Obligation' in the Bible

Now we who are strong have an obligation to bear the weaknesses of those without strength, and not to please ourselves.

For if I preach the gospel, I have no reason to boast, because an obligation is placed on me. And woe to me if I do not preach the gospel!

But I didn’t want to do anything without your consent, so that your good deed might not be out of obligation, but of your own free will.