John Mark
Mark 9:29ESV·traditional attribution

And he said to them, “This kind cannot be driven out by anything but prayer.”

Matthew Henry Presbyterian @wholebiblehenry

We have here the story of Christ casting the devil out of a child, somewhat more fully related than it was in Mat 17:14, etc. Observe here, I. Christ's return to his disciples, and the perplexity he found them in. He laid aside his robes of glory, and came to look after his family, and to enquire what was become of them.

Commenting on Mark 9:14-29

John Gill Reformed Baptist @doctorgill

And he said unto them,.... Matthew, besides the following reason, assigns another, as given by our Lord, why they could not cast out the foul spirit, which was their unbelief; of which they were guilty in some sort, as well as the Jews, and the father of the child; but Mark omits it, and only relates this as the reason; this kind can come forth...

Albert Barnes Presbyterian @notesbybarnes

Verse 29. (l) "by prayer" (m) "and fasting"