John Calvin Commentary 1 Corinthians 9:7

"What soldier ever serveth at his own charges? who planteth a vineyard, and eateth not the fruit thereof? Or who feedeth a flock, and eateth not of the milk of the flock?" — 1 Corinthians 9:7 (ASV)

Who hath gone a warfare at his own charges? It is the present tense that is used as meaning—is accustomed to go a warfare. I have, however, in order to lessen some of the harshness, rendered it in the preterite. Now, by three comparisons, and these also taken from common life, he demonstrates that it was allowable for him to live, if he chose, at the public expense of the Church, to show that he claims nothing for himself except what human nature itself teaches us is reasonable.

The first is taken from military law, for soldiers usually have their provisions furnished to them at the public expense. The second is taken from vine-dressers, for the farmer plants a vine—not to waste his efforts, but to gather the fruit. The third is taken from keepers of cattle, for the shepherd does not work for nothing, but eats of the milk of the flock—that is, he is supported from the produce.

As natural equity shows this to be reasonable, who will be so unjust as to refuse sustenance to the pastors of the Church? While it may happen that some serve as soldiers at their own expense (for example, the Romans in ancient times, when no tribute was yet paid and there were no taxes), this does not militate against Paul’s statement, for he simply takes his argument from common and universally accepted practice.