73 Both these counsels, therefore, must be accepted as having been spoken by the Lord to the apostles; namely, at once that they should not take a staff, and that they should take nothing save a staff only. For when He said to them, according to Matthew, “Provide neither gold nor silver, nor money in your purses, nor scrip for your journey, neither two coats, neither shoes, nor yet a staff,” He added immediately, “for the workman is worthy of his meat.” And by this He makes it sufficiently obvious why it is that He would have them provide and carry none of these things.
He shows that His reason was, not that these things are not necessary for the sustenance of this life, but because He was sending them in such a manner as to declare plainly that these things were due to them by those very persons who were to hear believingly the gospel preached by them; just as wages are the soldier's due, and as the fruit of the vine is the right of the planters, and the milk of the flock the right of the shepherds. For which reason Paul also speaks in this wise: “Who goes a warfare any time at his own charges?
Who plants a vineyard, and eats not of the fruit thereof? Who feeds a flock, and eats not of the milk of the flock?” For under these figures he was speaking of those things which are necessary to the preachers of the gospel. And so, a little further on, he says: “If we have sown unto you spiritual things, is it a great thing if we shall reap your carnal things? If others are partakers of this power over you, are not we rather? Nevertheless we have not used this power.” This makes it apparent that by these instructions the Lord did not mean that the evangelists should not seek their support in any other way than by depending on what was offered them by those to whom they preached the gospel (otherwise this very apostle acted contrary to this precept when he acquired a livelihood for himself by the labours of his own hands, because he would not be chargeable to any of them), but that He gave them a power in the exercise of which they should know such things to be their due.
Now, when any commandment is given by the Lord, there is the guilt of non-obedience if it is not observed; but when any power is given, any one is at liberty to abstain from its use, and, as it were, to recede from his right. Accordingly, when the Lord spoke these things to the disciples, He did what that apostle expounds more clearly a little further on, when he says, “Do ye not know that they who minister in the temple live of the things of the temple? And they which wait at the altar are partakers with the altar?
Even so has the Lord ordained, that they which preach the gospel should live of the gospel. But I have used none of these things.” When he says, therefore, that the Lord ordained it thus, but that he did not use the ordinance, he certainly indicates that it was a power to use that was given him, and not a necessity of service that was imposed upon him.
Source: The Harmony of the Gospels (New Advent)