Origen's Commentary on the Gospel of Matthew

Now the father of the epileptic—perhaps the angel to whom he had been allotted, if we are to say that every human soul is put in subjection to some angel—prays the Physician of souls for his son that He may heal him who could not be healed from his disorder by the inferior word which was in the disciples. But the dumb and deaf spirit, who was cast out by the Word, must be figuratively understood as the irrational impulses, even towards that which seems to be good, so that, what things any man once did by irrational impulse which seemed to onlookers to be good, he may do no longer irrationally but according to the reason of the teaching of Jesus. Under the inspiration of this Paul also said, “If I have all faith so as to remove mountains;” for he, who has all faith, which is as a grain of mustard seed, removes not one mountain only, but also several analogous to it; for although faith is despised by men and appears to be something very little and contemptible; yet when it meets with good ground, that is the soul, which is able fittingly to receive such seed, it becomes a great tree, so that no one of those things which have no wings, but the birds of heaven which are winged spiritually, are able to lodge in the branches of faith so great.