To get an understanding of that verse, let’s read Matthew 17:14-21, “And when they had come to the multitude, a man came to Him, kneeling down to Him and saying, “Lord, have mercy on my son, for he is an epileptic and suffers severely; for he often falls into the fire and often into the water.  So I brought him to Your disciples, but they could not cure him.” Then Jesus answered and said, “O faithless and perverse generation, how long shall I be with you? How long shall I bear with you? Bring him here to Me.” And Jesus rebuked the demon, and it came out of him; and the child was cured from that very hour. Then the disciples came to Jesus privately and said, “Why could we not cast it out?” So Jesus said to them, “Because of your unbelief; for assuredly, I say to you, if you have faith as a mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move; and nothing will be impossible for you. However, this kind does not go out except by prayer and fasting.” (NKJV)

In this incident, there is a man who brought his epileptic son to the Lord’s disciples so that they might heal him. When they could not heal him, the father brought his son to the Lord. The Lord, after rebuking the boy’s father and the crowd around them gave instant healing to the boy. The disciples were puzzled. Why could they not heal this young boy? The Lord told His disciples that they were hindered in their work because of their own unbelief! Perhaps in trying to heal this boy, they really didn’t think they could do it. Notice how the Lord blamed the disciples for their unbelief. Today’s so-called ‘faith healers’ will blame the ones desiring to be healed for a lack of faith if they cannot be healed. Here, the Lord put the blame on those attempting to do the healing.

Mark’s recounting of this event tells us that the disciples asked the Lord in private why they were not able to heal this boy. It must have been embarrassing and puzzling to them when they could not heal the boy. We read in Mark 9:28-29, “And when He had come into the house, His disciples asked Him privately, “Why could we not cast it out? So He said to them, “This kind can come out by nothing but prayer and fasting.” In order to function as a servant and representative of the Lord, it must be taken very seriously and will depend upon faith in the Lord to do whatever is His will to do. This kind of power to be a true servant of the Lord, is dependent on prayer and fasting. PRAYER shows our dependence on the Lord. FASTING shows our denial of self in order to be God’s servant. What is your desire? Do you want to serve the savior that delivered you from an eternal Hell? Do you want to honor that One who gave His life for you? Then commit your life to Him. Depend upon Him always and deny yourself always. (311.4)