Luke 11: 15 - 26
15 But some of them said, "He casts out demons by Be-el'zebul, the prince of demons";
16 while others, to test him, sought from him a sign from heaven.
17 But he, knowing their thoughts, said to them, "Every kingdom divided against itself is laid waste, and a divided household falls.
18 And if Satan also is divided against himself, how will his kingdom stand? For you say that I cast out demons by Be-el'zebul.
19 And if I cast out demons by Be-el'zebul, by whom do your sons cast them out? Therefore they shall be your judges.
20 But if it is by the finger of God that I cast out demons, then the kingdom of God has come upon you.
21 When a strong man, fully armed, guards his own palace, his goods are in peace;
22 but when one stronger than he assails him and overcomes him, he takes away his armor in which he trusted, and divides his spoil.
23 He who is not with me is against me, and he who does not gather with me scatters.
24 "When the unclean spirit has gone out of a man, he passes through waterless places seeking rest; and finding none he says, `I will return to my house from which I came.'
25 And when he comes he finds it swept and put in order.
26 Then he goes and brings seven other spirits more evil than himself, and they enter and dwell there; and the last state of that man becomes worse than the first."

EWTN