Mark 9:28

28 Afterward, when Jesus was alone in the house with his disciples, they asked him, “Why couldn’t we cast out that evil spirit?”

Mark 9:28 Meaning and Commentary

Mark 9:28

And when he was come into the house
Perhaps into the man's house whose child he had healed, or into some other in these parts, for the sake both of retirement and refreshment:

his disciples asked him privately, why could not we cast him out?
The nine disciples, who were particularly concerned in this matter, fearing they had lost the power of casting out devils, conferred upon them, inquired of Jesus, when he was alone, why they could not cast the demon out of the child, when they had ejected unclean spirits out of many others; (See Gill on Matthew 17:19).

Mark 9:28 In-Context

26 Then the spirit screamed and threw the boy into another violent convulsion and left him. The boy appeared to be dead. A murmur ran through the crowd as people said, “He’s dead.”
27 But Jesus took him by the hand and helped him to his feet, and he stood up.
28 Afterward, when Jesus was alone in the house with his disciples, they asked him, “Why couldn’t we cast out that evil spirit?”
29 Jesus replied, “This kind can be cast out only by prayer. ”
30 Leaving that region, they traveled through Galilee. Jesus didn’t want anyone to know he was there,