Then came the disciples to Jesus apart, and said, Why could not we cast him out?
All Commentaries on Matthew 17:19 Go To Matthew 17
Theophylact of Ochrid
AD 1107
The apostles were afraid that they had lost the grace against demons that had been given to them; this is why they asked Jesus in private and with great anxiety. But the Lord reproves them for being imperfect in faith, saying, "Because of your unbelief. For if you had fervent, ardent faith, you would accomplish great things even though they appeared to be small." The location of the mountains which the Apostles moved is nowhere recorded, yet it is likely that they did move them, but the event was not written down; for not everything was written down. Or, by another interpretation, they did not move a mountain because there had been no occasion to do so, but they did even greater things than that. Note how the Lord said, Ye shall say unto this mountain, Remove hence, in other words, the mountain shall move when you say the word. But the Apostles did not say the word as there was neither occasion nor necessity, and so they did not move mountains. But if indeed they had spoken, they would have moved. This kind of demon is cast out by prayer and fasting. For they themselves who are demonized must fast, as well as those who would heal them; then comes the prayer, preceded by fasting, not drunkenness. Understand, then, that even perfect faith is as the grain of mustard seed, considered worthless on account of the foolishness of the preaching. Yet if it should find good soil, it grows into a tree in which the winged creatures of heaven, that is, soaring thoughts, may alight. Whoever, then, has perfect faith can say to this mountain, that is, to the demon, Remove hence. For Christ was also referring to the demon that had gone out.
