1 Corinthians 9:6-8

Or is it only Barnabas and I who have no right to refrain from doing manual labor for a livelihood [in order to go about the work of the ministry]? [Consider this:] What soldier at any time serves at his own expense? Who plants a vineyard and does not eat any of the fruit of it? Who tends a flock and does not partake of the milk of the flock? Do I say this only on human authority and as a man reasons? Does not the Law endorse the same principle?