Mark 9:19

III. The rebuke he gave to them all (v. 19); O faithless generation, how long shall I be with you? How long shall I suffer you? Dr. Hammond understands this as spoken to the disciples, reproving them for not exerting the power he had given them, and because they did not fast and pray, as in some cases he had directed them to do. But Dr. Whitby takes it as a rebuke to the scribes, who gloried in this disappointment that the disciples met with, and hoped to run them down with it. Them he calls a faithless generation, and speaks as one weary of being with them, and of bearing with them. We never heard him complaining, "How long shall I be in this low condition, and suffer that?" But, "How long shall I be among these faithless people, and suffer them?"

Verses 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.