Mark 9:28,29

(28) And when he was come into the house, his disciples asked him privately, Why could not we cast him out? (29) And he said unto them, This kind can come forth by nothing, but by prayer and fasting.

I have separated those verses, from the preceding, though they form a part of the same history; not by way of explaining them, for very freely confess, that I do not apprehend the full sense and meaning of them: but by way of calling the Reader's attention to them, one point I think is very evident from our LORD's words, that when the disciples questioned the cause of their inability, our LORD doth not say, this kind can come forth by nothing but by prayer and fasting: in allusion to the evil spirit, for in the parallel passage, Matthew 17:20. JESUS directly refers it to a want of faith. Fastings and prayers are creature exercises. Our LORD cannot be supposed to assign to such the power of miracles. And evidently in the parallel passage of Matthew, the LORD ascribes the power rather to faith. The subject is however attended with too much difficulty to determine. Though I am inclined to think that by prayer and fasting, JESUS refers to himself, in whom alone all righteousness is fulfilled.