פירוש על קידושין 61:11

And if this is [related about] one who is not commanded, and he performs it: [That] the Holy One, blessed be He, paid him his reward.

According to R. Hanina, a person who fulfills a commandment even out of obligation is greater than one who fulfills it not out of obligation. This, I think, is somewhat counterintuitive. Most of us think that when we do something because we want to, we are in some way better than those who fulfill it because they have to. That is, I think, R. Hanina’s point. Fulfilling commandments out of a sense of obligation shows a commitment not just to the particular deed, but to its source.