He saw a great multitude around them. The disciples were, no doubt, held up to public gaze, as the enemies of the truth are wont, on occasions of triumph, to assemble a crowd about a trifle. The scribes had made such a noise about it, as to draw down on the disciples the ridicule of many persons. And yet it appears that there were some who were not ill disposed; for, as soon as they see Jesus, they salute him; and even the insolence of the scribes is restrained by his presence, for, when they are asked what is the matter in dispute, they have not a word to say. As Mark is more full, and explains the circumstances very minutely, we shall follow the order of his narrative. And first he points out clearly the reason why Christ uses a harshness so unusual with him, when he exclaims that the Jews, on account of their perverse malice, do not deserve to be any longer endured. We know how gently he was wont to receive them, even when their requests were excessively importunate. A father here entreats in behalf of an only son, the necessity is extremely urgent, and a modest and humble appeal is made to the compassion of Christ. Why then does he, contrary to his custom, break out suddenly into passion, and declare that they can be endured no longer? As the narrative of Matthew and Luke does not enable us to discover the reason of this great severity, some commentators have fallen into the mistake of supposing that this rebuke was directed either against the disciples, or against the father of the afflicted child. But if we duly consider all the circumstances of the case, as they are related by Mark, there will be no difficulty in arriving at the conclusion, that the indignation of Christ was directed against the malice of the scribes, and that he did not intend to treat the ignorant and weak with such harshness. During Christ's absence, a lunatic child had been brought forward. The scribes, regarding this as a plausible occasion for giving annoyance, seized upon it eagerly, and entreated the disciples that, if they had any power, they would exercise it in curing the child. It is probable that the disciples made an attempt, and that their efforts were unavailing; upon which the scribes raise the shout of victory, and not only ridicule the disciples, but break out against Christ, as if in their person his power had been baffled. It was an extraordinary display of outrageous impiety united with equally base ingratitude, maliciously to keep out of view so many miracles, from which they had learned the amazing power of Christ; for they manifestly endeavored to extinguish the light which was placed before their eyes. With good reason, therefore, does Christ exclaim that they could no longer be endured, and pronounce them to be an unbelieving and perverse nation; for the numerous proofs which they had formerly beheld ought at least to have had the effect of preventing them from seeking occasion of disparagement.

See this passage explained in the notes at Matthew 17:14-21.

Questioning with them - Debating with the disciples, and attempting to confound them. This he saw as he came down from the mount. In his absence they had taken occasion to attempt to perplex and confound his followers.

(4) And when he came to [his] disciples, he saw a great multitude about them, and the scribes questioning with them.
(4) Christ shows by a miracle, even to the unworthy, that he has come to restrain the wrath of Satan.

And when he came to his disciples,.... The other nine, who were left at the bottom of the mountain, and were waiting for him:
he saw a great multitude about them: there was a multitude that followed him from Bethsaida hither; and which, very likely, was greatly increased upon Christ's arrival in those parts, and the people hearing of it;
and the Scribes questioning with them; disputing and contending with them about their master, his doctrines and miracles, and their mission and authority from him; insulting them, on account of their inability to dispossess a dumb spirit, hereafter related.

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.

HEALING OF A DEMONIAC BOY--SECOND EXPLICIT ANNOUNCEMENT OF HIS APPROACHING DEATH AND RESURRECTION. ( = Matthew 17:14-23; Luke 9:37-45). (Mark 9:14-32)
And when he came to his disciples, he saw a great multitude about them, and the scribes questioning with them--This was "on the next day, when they were come down from the hill" (Luke 9:37). The Transfiguration appears to have taken place at night. In the morning, as He came down from the hill on which it took place--with Peter, and James, and John--on approaching the other nine, He found them surrounded by a great multitude, and the scribes disputing or discussing with them. No doubt these cavillers were twitting the apostles of Jesus with their inability to cure the demoniac boy of whom we are presently to hear, and insinuating doubts even of their Master's ability to do it; while they, zealous for their Master's honor, would no doubt refer to His past miracles in proof of the contrary.

And when he came to his disciples. After the transfiguration.
He saw a great multitude. For notes on this miracle, see Matthew 17:14-21. Compare Luke 9:37-42. Mark's account is the fullest. According to the Revision, Matthew says that the youth was an epileptic, and the symptoms given by Mark are those of epilepsy. Mark also states that he had been afflicted from childhood.

Matthew 17:14; Luke 9:37.