Origen's Commentary on the Gospel of Matthew

But when the Saviour said, “O faithfulness and perverse generation,” He signifies that wickedness, which is contrary to nature, stealthily enters in from perversity, and makes us perverted. But of the whole race of men on earth, I think, being oppressed by reason of their wickedness and His tarrying with them, the Saviour said, “How long shall I be with you?” We have already, then, spoken in part of the words, “If ye have faith as a grain of mustard seed, ye shall say unto this mountain,” etc.; but nevertheless also we shall speak in this place the things that appear to us fitted to increase perspicuity. The mountains here spoken of, in my opinion, are the hostile powers that have their being in a flood of great wickedness, such as are settled down, so to speak, in some souls of men. Whenever, then, any one has all faith so that he no longer disbelieves in any things which are contained in the Holy Scriptures, and has faith such as was that of Abraham, who believed in God to such a degree that his faith was counted for righteousness. he has all faith as a grain of mustard seed; then will such an one say to this mountain—I mean, the dumb and deaf spirit in him who is called lunatic,—“Remove hence,” clearly, from the man who is suffering, perhaps to the abyss, and it shall remove. And the Apostle, taking, I think. his starting-point from this place, says with apostolical authority, “If I have all faith so as to remove mountains,” for not one mountain merely, but also several analogous to it, he removes who has all faith which is as a grain of mustard-seed; and nothing shall be impossible to him who has so great faith. But let us also attend to this, “This kind goeth not out save by prayer and fasting,” in order that if at any time it is necessary that we should be engaged in the healing of one suffering from such a disorder, we may not adjure, nor put questions, nor speak to the impure spirit as if it heard, but devoting ourselves to prayer and fasting, may be successful as we pray for the sufferer, and by our own fasting may thrust out the unclean spirit from him.