21 And Jesus asked his father, "How long has he had this?" And he said, "From childhood. 22 And it has often cast him into the fire and into the water, to destroy him; but if you can do anything, have pity on us and help us." 23 And Jesus said to him, "If you can! All things are possible to him who believes." 24 Immediately the father of the child cried out and said, "I believe; help my unbelief!" 25 And when Jesus saw that a crowd came running together, he rebuked the unclean spirit, saying to it, "You dumb and deaf spirit, I command you, come out of him, and never enter him again." 26 And after crying out and convulsing him terribly, it came out, and the boy was like a corpse; so that most of them said, "He is dead." 27 But Jesus took him by the hand and lifted him up, and he arose.
Matthew Henry's Commentary on Mark 9:21-27
Commentary on Mark 9:14-29
(Read Mark 9:14-29)
The father of the suffering youth reflected on the want of power in the disciples; but Christ will have him reckon the disappointment to the want of faith. Very much is promised to our believing. If thou canst believe, it is possible that thy hard heart may be softened, thy spiritual diseases may be cured; and, weak as thou art, thou mayest be able to hold out to the end. Those that complain of unbelief, must look up to Christ for grace to help them against it, and his grace will be sufficient for them. Whom Christ cures, he cures effectually. But Satan is unwilling to be driven from those that have been long his slaves, and, when he cannot deceive or destroy the sinner, he will cause him all the terror that he can. The disciples must not think to do their work always with the same ease; some services call for more than ordinary pains.