Matthew Poole and continuators on Matthew 17:18

18 And Jesus rebuked the devil, and he departed out of him, and the child was cured from that very hour.

Mark relates this part of the History, much more largely, Ch. 9.19.20, 21, 22, 23, 24, 25, 26, 27. He answered him, and said, O Faithless Generation, how long shall I be with you? How long shall I suffer you? Bring him unto me. And they brought him unto him, and when he saw him, straightway the Spirit tare him, and he fell on the Ground, and wallowed Foaming: And he asked his Father, how long is it ago, since this came unto him? And he said of a Child. And oft times, it hath cast him into the Fire, and into the Waters to destroy him: But if thou canst do any thing, have Compassion on us, and help us. Iesus saith unto him: If thou canst believe, all things are possible to him that believeth. And straightway the Father of the Child cryed out, and said, with Tears, Lord I believe, help my unbelief. When Iesus saw, that the People came running together, he rebuked the foul Spirit, saying unto him: Thou Dumb and Deaf Spirit, I Charge thee come out of him, and enter no more into him. And the Spirit cryed, and rent him sore and came out of him, and he was as one Dead. Insomuch, that many said; He is Dead. But Iesus took him by the Hand, and lifted him up, and he arose. Luke relates this shorter, but addeth nothing to what is in the other Evangelists, Luk. 9.41, 42. Then Iesus answered, and said, O Faithless, and perverse Generation. Christ here calls them, not so with respect to justifying Faith, but that Faith which respected the Divine Power, as to working Miracles. Every Revelation of the Divine Will, is the Object of Faith, Christ had revealed to the Iews, that he was sent of God, and furnished with such a Power, this the Iews and particularly the Scribes did not believe, the Faith of the Father of this Child, was but very weak in the Case; no more, as we shall see afterwards, was the Faith of the Disciples, so as he may be understood to respect them all, tho in different Degrees, he calls them Perverse, because they had so often seen, and experienced his Power of this Nature, yet their Faith was not clear, and strong. He biddeth that the young Man should be brought to him, and it was done. And when he saw him (saith Mark) straightway, the Spirit tare him, &c. Our Saviour could easily have prevented this, but probably he suffered it, that the Miracle might be more Evident. However it letteth us see, how hardly the Devil parteth with his Possession in us, in any Degree, and how ready he is to run to the length of his Line, in doing us Mischief. Christ asked his Father, how long he had been so vexed, his Father tells him from a Child. By this also the Miracle was more Illustrious, which probably was the reason; why Christ propounded the Question: No Evils are too inveterate for Christ to remove. The Father reneweth his request, and in it sheweth the Weakness of his Faith, If saith he, thou canst do any thing, his coming to Christ, and Crying to him, argued that he believed, he could do something, his Saying, If thou canst do any thing, speaks the Weakness of his Faith. Christ tells him, If he could believe all things are possible. Nothing tyeth Gods hands, but his Creatures unbelief. It is said, That Christ could not in Capernaum, do many mighty works, because of their unbelief. Upon this the Father Crys out, Lord I believe, help my Vnbelief. Men may truly believe, and yet have a mixture of Unbelief. God rewards a weak Faith, to Souls labouring under the Sense of their Weakness, and desiring an increase of strength, Christ rebukes the Spirit (called a Dumb and Deaf Spirit, because it made the Person such that was thus affected with it) Christ commands the Spirit out, and so to come out, as never more to enter into him. The Evil Spirit roars, rendeth him, comes out, and leaveth him as one dead: Which still confirmeth us in his Malice to mankind, he will do what harm he can, when he cannot do us the harm he would.