Matt. X. 16.
“Behold, I send you forth as sheep in the midst of wolves; be ye therefore wise as serpents, and harmless as doves.”
Having made them feel confident about their necessary food, and opened unto them all men's houses, and having invested their entrance with an appearance to attract veneration, charging them not to come in as wanderers, and beggars, but as much more venerable than those who received them (for this He signifies by His saying, “the workman is worthy of his hire;” and by His commanding them to inquire, who was worthy, and there to remain, and enjoining them to salute such as receive them; and by His threatening such as receive them not with those incurable evils): having I say, in this way cast out their anxiety, and armed them with the display of miracles, and made them as it were all iron and adamant, by delivering them from all worldly things, and enfranchising them from all temporal care: He speaks in what follows of the evils also that were to befall them; not only those that were to happen soon after, but those too that were to be in long course of time; from the first, even long beforehand, preparing them for the war against the devil. Yea, and many advantages were hence secured; and first, that they learned the power of His foreknowledge; secondly, that no one should suspect, that through weakness of their Master came these evils upon them; thirdly, that such as undergo these things should not be dismayed by their falling out unexpectedly, and against hope; fourthly, that they might not at the very time of the cross be troubled on hearing these things. For indeed, they were just so affected at that time; when also He upbraided them, saying, “Because I have said these things unto you, sorrow has filled your hearts; and none of you asks me, where are You going?” And yet He had said nothing as yet touching Himself, as that He should be bound, and scourged, and put to death, that He might not hereby also confound their minds; but for the present He announces before what should happen to themselves.
Then, that they might learn that this system of war is new, and the manner of the array unwonted; as He sends them bare, and with one coat, and unshod, and without staff, and without girdle or scrip, and bids them be maintained by such as receive them; so neither here did He stay His speech, but to signify His unspeakable power, He says, Even thus setting out, exhibit the gentleness of “sheep,” and this, though you are to go unto “wolves;” and not simply unto wolves, but “into the midst of wolves.”
And He bids them have not only gentleness as sheep, but also the harmlessness of the dove. “For thus shall I best show forth my might, when sheep get the better of wolves, and being in the midst of wolves, and receiving a thousand bites, so far from being consumed, do even work a change on them a thing far greater and more marvellous than killing them, to alter their spirit, and to reform their mind; and this, being only twelve, while the whole world is filled with the wolves.”
Let us then be ashamed, who do the contrary, who set like wolves upon our enemies. For so long as we are sheep, we conquer: though ten thousand wolves prowl around, we overcome and prevail. But if we become wolves, we are worsted, for the help of our Shepherd departs from us: for He feeds not wolves, but sheep: and He forsakes you, and retires, for neither do you allow His might to be shown. Because, as He accounts the whole triumph His own, if you being ill used, show forth gentleness; so if you follow it up and give blows, you obscure His victory.
Source: Homilies on the Gospel of St. Matthew (New Advent)