Matthew 12:27

And if I by Beelzebub cast out demons, by whom do your sons cast them out? therefore shall they be your judges.

Christ here referred to the widespread practice of some of the disciples (sons) of the Pharisees of casting out demons, or pretending to do so, which practice the Pharisees openly accepted, and upon which they based claims of divine approval of both themselves and their doctrines. Josephus described such a case thus:

I have seen a certain man of my own country, whose name was Eleazer, releasing people that were demoniacal, in the presence of Vespasian and his sons and captains. He put a ring to the nostrils of the demoniac, and drew the demon out through his nostrils, making mention of Solomon, and reciting the incantations which he composed.[5]

Christ's argument was: You Pharisees accept so-called exorcisms by your disciples, in spite of all the "mumbo jumbo" and evident witchcraft connected with them, but you reject my miracles which are accomplished with only a word of authority. If the miracles of your disciples are acceptable, surely mine, the Christ's, should also be acceptable. Of course, Christ did not endorse the exorcisms of the Pharisees' disciples any more than he endorsed the Pharisees.