1 Corinthians 9:7
Who goeth a warfare any time at his own charges? who planteth a vineyard, and eateth not of the fruit thereof? or who feedeth a flock, and eateth not of the milk of the flock?
Note 1 at 1Co 9:7: Paul used a series of illustrations to strengthen his point (1Co 9:4 and 6) that he had the right, or power, to derive his living from the Gospel if he wanted to. Soldiers don't have to maintain themselves. All their needs are met by the government. Those who work in vineyards get to eat freely of the fruit they are harvesting. Shepherds get to drink the milk from their flocks. In any kind of profession, workers have the right to their wages. Therefore, it is right for ministers to live from the proceeds of preaching the Gospel.