And they brought him unto him. The father, it would seem, was not able of himself to bring him, so fierce and violent were the paroxysms of the disorder. And when he saw him, straightway the spirit tare him ( συνεσπέραξεν)—it might be rendered, convulsed him—grievously. Observe the Greek construction ( καὶ ἰδὼν αὐτὸν τὸ πνεῦμα), masculine participle with neuter noun. The sight of Christ stirred the evil spirit dwelling in the child. He was irritated by the presence of Christ; for he knew his power, and feared lest he should be cast out. Then came the last and most violent convulsion. He wallowed foaming. The word "to wallow" is probably from the Latin volvo. He rolled about in his agony. St. Gregory, quoted by Trench, shows how true all this is to nature; and that "the expulsion of a deadly evil from our spiritual being is not accomplished without a terrible struggle, followed in some cases by extreme prostration."
Our Lord asks the father, not the sufferer, which in this case would have been useless—he was but a lad, and he was dumb. Our Lord's question, How long time is it since this hath come unto him? was intended, not of course for his own information, but to inspire the father with hope and confidence. The father briefly answers, From a child; and then turns to a description of the perils to which his child was continually exposed through these paroxysms. And then, half doubting, half in despair, he says, If thou canst do anything, have compassion on us, and help us. It is as though he said, "Thy disciples have failed, perhaps thy power may be greater."
The most approved reading here is, not εἴ δύνασαι πιστεῦσαι, but simply εἴ δύνασαι, So that the English rendering is, If thou canst! All things are possible to him that believeth. Our Lord takes up the father's words. It is as though he said, "Thou sayest to me, 'If thou canst do anything!' Ah, that 'If thou canst!' All things are possible to him that believeth." In other words, our Lord said to him, "Believe in me, and your child shall be healed." It was right that Christ should demand faith in himself; for it was not fitting that he should confer his special benefits on those who disbelieved or doubted about him—that he should thrust his blessings on those who were unworthy of them. The answer of the father is touching and beautiful. Greatly agitated, he cried out and said (we might well suppose ( μετὰ δακρύων "with tears," although the weight of evidence is against this addition being retained in the text), I believe; help thou mine unbelief. It is as though he said," I do believe; but my faith is weak. Do thou, therefore, increase and strengthen it; so that whatever there is in me of doubt or remaining unbelief may be taken away, and I may be counted worthy to obtain from thee this blessing for my son." Nor can we doubt that Christ heard a prayer so humble and so fervent, and took away from him the last remains of doubt and unbelief.