Jesus asked this to show that the charge against Him defeated itself. Some said He cast out devils by the chief of the devils, and others tested Him by asking for a sign from heaven (Luke 11:15-16). Knowing their thoughts, He reminded them that "every kingdom divided against itself is brought to desolation" (Luke 11:17). If Satan were helping Jesus throw Satan's own servants out, Satan would be fighting himself. Barnes, whose note on Luke sends the reader to his notes on Matthew 12, puts it plainly: "A kingdom, or a family, can prosper only by living in harmony," and if the charge were true, "Satan must have less than human prudence." Gill says the point is that "Satan must be against himself, if what the Pharisees said was true."

Jesus answered His own question. A divided kingdom cannot stand, so the charge fails. He pressed a second question about their own exorcists (Luke 11:19) and then gave the true explanation: "But if I with the finger of God cast out devils, no doubt the kingdom of God is come upon you" (Luke 11:20). He pictured a strong man overcome by "a stronger than he" (Luke 11:21-22) and warned, "He that is not with me is against me" (Luke 11:23). Luke records no reply from those who made the charge.

Beelzebub was a name for "the chief of the devils" (Luke 11:15). Gill notes that several copies read "Beelzebul," which is the spelling the ESV uses.

Luke does not name the accusers. He says only "some of them" (Luke 11:15), meaning some of the people who had just seen the healing. Matthew says it was the Pharisees (Matthew 12:24), and Mark says it was "the scribes which came down from Jerusalem" (Mark 3:22). Gill reads Luke's "some of them" as the Pharisees, who, he says, "could not bear that he should be thought to be the Messiah."

This question shows that Jesus is not one more player inside Satan's kingdom. He is the One overthrowing it. Satan is pictured as "a strong man armed" who keeps his palace, but "a stronger than he" comes, overcomes him, and divides his spoils (Luke 11:21-22). Matthew Henry calls it "an allowed maxim, confirmed by every day's experience, that no interest can stand that is divided against itself."

The miracle itself was the answer. A man who could not speak now spoke (Luke 11:14). Henry says that calling this work the "finger" of God "perhaps may intimate how easily Christ did and could conquer Satan." The same deed that some called devilish was a sign that "the kingdom of God is come upon you" (Luke 11:20).