17 One of the men in the crowd spoke up and said, "Teacher, I brought my son so you could heal him. He is possessed by an evil spirit that won't let him talk. 18 And whenever this spirit seizes him, it throws him violently to the ground. Then he foams at the mouth and grinds his teeth and becomes rigid. So I asked your disciples to cast out the evil spirit, but they couldn't do it." 19 Jesus said to them, "You faithless people! How long must I be with you? How long must I put up with you? Bring the boy to me." 20 So they brought the boy. But when the evil spirit saw Jesus, it threw the child into a violent convulsion, and he fell to the ground, writhing and foaming at the mouth. 21 "How long has this been happening?" Jesus asked the boy's father. He replied, "Since he was a little boy. 22 The spirit often throws him into the fire or into water, trying to kill him. Have mercy on us and help us, if you can." 23 "What do you mean, 'If I can'?" Jesus asked. "Anything is possible if a person believes." 24 The father instantly cried out, "I do believe, but help me overcome my unbelief!" 25 When Jesus saw that the crowd of onlookers was growing, he rebuked the evil spirit. "Listen, you spirit that makes this boy unable to hear and speak," he said. "I command you to come out of this child and never enter him again!" 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."
Matthew Henry's Commentary on Mark 9:17-26
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.