Charles Ellicott Commentary Matthew 17:19

"Then came the disciples to Jesus apart, and said, Why could not we cast it out?" — Matthew 17:19 (ASV)

Why could we not cast him out? This question obviously came from the disciples who had been left below when our Lord went apart with Peter, James, and John to the Mount of Transfiguration. Even now, they did not see the reason for their failure. They had dealt with this case as they had with others; why had they not achieved a similar result?

They did not yet realize that our Lord’s words of rebuke applied to them, and they did not consider themselves part of the “faithless generation.”