To cast it out.
But they were
To do so.”
καὶ εἶπα τοῖς μαθηταῖς σου ἵνα αὐτὸ ἐκβάλωσιν, καὶ οὐκ ἴσχυσαν.
The story of the man with the incurable son can be found in all 3 synoptic gospels, Matthew, chapter 17:16, Luke, chapter 9:40, and here in Mark. Then there was the kicker, Mark, like the other gospel writers, indicated that this man had asked Jesus’s disciples (καὶ εἶπα τοῖς μαθηταῖς σου) to cast out this spirit from his son (ἵνα αὐτὸ ἐκβάλωσιν), but they did not have the ability to do so (καὶ οὐκ ἴσχυσαν). Why were the disciples of Jesus unable to cure his son?