John Calvin Commentary 1 Corinthians 9:17

"For if I do this of mine own will, I have a reward: but if not of mine own will, I have a stewardship intrusted to me." — 1 Corinthians 9:17 (ASV)

For if I do this thing willingly: here, reward means what the Latins call operae pretium (recompense for labor), and what he had previously called glorying. Others, however, interpret it differently—as meaning that a reward is set before all who discharge their duty faithfully and heartily.

But, for my part, I understand the man who does this thing willingly, to be one who acts with such cheerfulness that, with edifying as his primary goal, he refuses nothing he knows will benefit the Church. On the other hand, he calls those unwilling who, in their actions, do indeed submit to necessity but act grudgingly because it is not from inclination.

For it always happens that the man who undertakes any business with zeal is also prepared of his own accord to submit to everything, the omission of which would hinder the work's completion. Thus Paul, being one who acted willingly, did not teach in a merely perfunctory manner but left nothing undone that he knew was suited to promote and further his doctrine. This then was his recompense for labor, and this his ground of glorying—that with a ready mind he relinquished his right, applying himself to fulfilling his office willingly and with fervent zeal.

But if unwillingly, a dispensation is committed to me. In whatever way others explain these words, the natural meaning, in my opinion, is this: God does not at all approve of the service done by the man who performs it grudgingly and, so to speak, with a reluctant mind. Therefore, whenever God has commanded us to do anything, we are mistaken if we think we have fulfilled it correctly when we perform it grudgingly. For the Lord requires that his servants be cheerful (2 Corinthians 9:7), so that they delight in obeying him and show their cheerfulness by the promptness with which they act. In short, Paul means that he would act in accordance with his calling only if he performed his duty willingly and cheerfully.