3 And after that He had said, “By whom do your children cast them out?” to show that in them it was His grace, not their own desert; He says, “Or else how can one enter into a strong man's house and spoil his goods, except He first bind the strong man, and then He will spoil his house?” Your children, says He, who either have already believed in Me, or who shall yet believe, and cast out devils, not through the prince of the devils, but through the simplicity of holiness, who assuredly either once were, or still are what you are also, sinners and ungodly; and so in the house of the devil, and the vessels of the devil, how could they be rescued from him whom he held so firmly through the iniquity which reigned over them, unless he were bound by the chains of My justice, that I might take away from him his vessels which once were vessels of wrath, and make them vessels of mercy?
This it is which the blessed Apostle also says when he rebukes the proud, and those who boast as it were of their own deserts, “For who makes you to differ?” That is, who makes you to differ from the mass of perdition derived from Adam and from the vessels of wrath. And that no man might say, “My own righteousness,” he says, “What have you, that you did not receive?” And on this point he says of himself also, “We also once were by nature the children of wrath, even as others.” So then he himself was a vessel in the house of that strong one, strong in evil, when he was a persecutor of the Church, a “blasphemer, injurious, living in malice and envy,” as he confesses. But He who bound the strong one, took away from him this vessel of perdition, and made it a vessel of election.
Source: Sermons on Selected Lessons of the New Testament (New Advent)