Matthew 12:25-26.
“And Jesus knew their thoughts, and said unto them, Every kingdom divided against itself shall be brought to desolation; and every city or house divided against itself, shall not stand: and if Satan cast out Satan, he is divided against himself; how shall then his kingdom stand?”
Even before now they had accused Him of this, that “by Beelzebub He casts out the devils.” But whereas then He did not rebuke them, allowing them both to know His power by His more numerous miracles, and by His teaching to learn His majesty: now, since they continued saying the same, He proceeds also to rebuke them, showing His Godhead by this first, that He made their secrets public; and secondly, by the very act of casting out the devils with ease.
And indeed the accusation too was very shameless. Because, as I have said, envy seeks not what to say, but only that it may say somewhat. Yet for all that, not even so did Christ despise them, but defends Himself with the forbearance proper to Him, teaching us to be meek to our enemies; and though they say such things, as we are neither conscious of, nor have they any the least probability, not to be disturbed, nor troubled, but with all long suffering to render them an account. This then He did most especially on that very occasion, affording the strongest proof, that the things were false that were said by them. For neither was it a demoniac's part to exhibit so much meekness; it was not a demoniac's part to know men's secrets.
For, in truth, both because of the exceeding impudence of such a suspicion, and because of the fear of the multitude, they dared not publicly make these charges, but were turning them in their mind. But He, to show them that He knew all that likewise, does not set down the accusation, nor does He expose their wickedness; but the refutation He adds, leaving it to the conscience of them that had said it to convict them. For on one thing only was He bent, to do good to them that were sinning, not to expose them.
Yet surely, if He had been minded to extend his speech in length, and to make them ridiculous, and withal to have exacted of them also the most extreme penalty, there was nothing to hinder Him. Nevertheless He put aside all these things, and looked to one object only, not to render them more contentious, but more candid, and so to dispose them better toward amendment.
How then does He plead with them? Not by allegation out of the Scriptures (for they would not so much as attend, but were sure rather to distort their meaning), but by the events of ordinary life. For “every kingdom,” says He, “divided against itself shall not stand; and a city and a house, if it be divided, is soon dissolved.”
For the wars from without are not so ruinous as the civil ones. Yea, and this is the case in bodies too; it is the case even in all things; but for this time He takes His illustration from those that are more publicly known.
And yet, what is there more powerful on earth than a kingdom? Nothing, but nevertheless it perishes if in dissension. And if in that case one throw the blame on the great burden of the affairs thereof, as breaking down by its own weight; what would you say of a city? And what of a house? Thus, whether it be a small thing, or a great, if at dissension with itself, it perishes. If then I, having a devil, do by him cast out the devils, there is dissension and fighting among devils, and they take their stand one against another. But if they stand one against another, their strength is wasted and destroyed. “For if Satan cast out Satan” (and He said not “the devils,” implying their great unanimity one with another), “he is then divided against himself;” so He speaks. But if he be divided, he has become weaker, and is ruined; and if he be ruined, how can he cast out another?
Do you see how great the absurdity of the accusation, how great the folly, the inconsistency? Since it is not for the same persons to say first, that He stands, and casts out devils, and then to say, that He stands by that, which it was likely would be the cause of His undoing.
Source: Homilies on the Gospel of St. Matthew (New Advent)