Mark 9:28 KJV

And when he was come into the house, his disciples asked him privately, Why could not we cast him out?
Mark 9:28, King James Version

In context

27 But Jesus took him by the hand, and lifted him up; and he arose.

28 And when he was come into the house, his disciples asked him privately, Why could not we cast him out?

29 And he said unto them, This kind can come forth by nothing, but by prayer and fasting.