Charles Spurgeon Commentary Mark 9:23-29

"And Jesus said unto him, If thou canst! All things are possible to him that believeth. Straightway the father of the child cried out, and said, I believe; help thou mine unbelief. And when Jesus saw that a multitude came running together, he rebuked the unclean spirit, saying unto him, Thou dumb and deaf spirit, I command thee, come out of him, and enter no more into him. And having cried out, and torn him much, he came out: and [the boy] became as one dead; insomuch that the more part said, He is dead. But Jesus took him by the hand, and raised him up; and he arose. And when he was come into the house, his disciples asked him privately, [How is it] that we could not cast it out? And he said unto them, This kind can come out by nothing, save by prayer." — Mark 9:23-29 (ASV)

If you can believe, all things are possible to him who believes. And straightway the father of the child cried out, and said with tears, Lord, I believe; help my unbelief. When Jesus saw that the people came running together, he rebuked the foul spirit, saying to him, You dumb and deaf spirit, I charge you, come out of him, and enter no more into him. And the spirit cried, and rent him sore, and came out of him: and he was as one dead, insomuch that many said, He is dead. But Jesus took him by the hand, and lifted him up; and he arose. And when he was come into the house, his disciples asked him privately, Why could we not cast him out?

And he said to them, This kind can come forth by nothing, but by prayer and fasting.

There are some things that we are not fit to do until we have drawn very near to God, have been deeply humbled, and, with sincere repentance, and the gracious operation of the Holy Spirit, have been cleansed so as to receive such a great blessing. Faith alone will not accomplish everything. Faith must be accompanied by prayer, and prayer must, at least sometimes in special cases, be attended with fasting. The Lord keeps reserves of His mercies, which He does not give immediately, even to the request of faith; He demands importunity on our part, and heart-searching, and heart-cleansing, before the blessing will be bestowed.