Theophylact of Ohrid
Catena Aurea · Markusevangelium 3
And he called them unto him, and said unto them in parables, How can Satan cast out Satan? And if a kingdom be divided against itself, that kingdom cannot stand. And if a house be divided against itself, that house cannot stand. And if Satan rise up against himself, and be divided, he cannot stand, but hath an end. No man can enter into a strong man’s house, and spoil his goods, except he will first bind the strong man; and then he will spoil his house. Verily I say unto you, All sins shall be forgiven unto the sons of men, and blasphemies wherewith soever they shall blaspheme: But he that shall blaspheme against the Holy Ghost hath never forgiveness, but is in danger of eternal damnation: Because they said, He hath an unclean spirit.
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?