Origen
Catena Aurea · Matthäusevangelium 17
Then came the disciples to Jesus apart, and said, Why could not we cast him out? And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you. Howbeit this kind goeth not out but by prayer and fasting.
If then we shall ever be required to be employed in the healing of those who are suffering any thing of this sort, we shall not adjure them, nor ask them questions, nor even speak, as though the unclean spirit could hear us, but by our fasting and our prayers drive away the evil spirits.