Mark 3:27

The "strong man" in this passage means the devil who was able to hold the human race in bondage. By his "goods," which Christ was coming to plunder, the devil was keeping for himself those who would in time become faithful, but had remained in the clutches of ungodliness and various sins. It was for the purpose of binding up this strong man that John, in the Apocalypse, saw "an angel coming down from heaven, having the key of the abyss and a great chain in his hand. And he laid hold on the dragon, the ancient serpent, who is the devil and Satan, and bound him for a thousand years." The angel checked and repressed his power to seduce and possess those destined to be set free.

(in Marc. i. 17) The Lord has also bound the strong man, that is, the devil: which means, He has restrained him from seducing the elect, and entering into his house, the world; He has spoiled his house, and his goods, that is men, because He has snatched them from the snares of the devil, and has united them to His Church. Or, He has spoiled his house, because the four parts of the world, over which the old enemy had sway, He has distributed to the Apostles and their successors, that they may convert the people to the way of life.

The meaning of the example is this: The devil is the strong man; his goods are the men into whom he is received; unless therefore a man first conquers the devil, how can he deprive him of his goods, that is, of the men whom he has possessed? So also I who spoil his goods, that is, free men from suffering by his possession, first spoil the devils and vanquish them, and am their enemy. How then can ye say that I have Beelzebub, and that being the friend of the devils, I cast them out?

(non occ.) And because He has already shown by an example that a devil cannot cast out a devil, He shows how he can be expelled, saying, No man can enter into a strong man's house, &c.