In Mark 9:14-29, it says
And when he came to his disciples, he saw a great multitude about them, and the scribes questioning with them. And straightway all the people, when they beheld him, were greatly amazed, and running to him saluted him. And he asked the scribes, What question ye with them? And one of the multitude answered and said, Master, I have brought unto thee my son, which hath a dumb spirit; And wheresoever he taketh him, he teareth him; and he foameth, and gnasheth with his teeth, and pineth away; and I spake to thy disciples that they should cast him out; and they could not. He answered him, and saith, O faithless generation, how long shall I be with you? how long shall I suffer you? bring him unto me. And they brought him unto him; and when he saw him, straightway the spirit tare him; and he fell on the ground, and wallowed foaming. And he asked his father, How long is it ago since this came unto him? And he said, Of a child. And ofttimes it hath cast him into the fire, and into the waters, to destroy him; but if thou canst do any thing, have compassion on us, and help us. Jesus said unto him, If thou canst believe, all things are possible to him that believeth. And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief. When Jesus saw that the people came running together, he rebuked the foul spirit, saying unto him, Thou dumb and deaf spirit, I charge thee, 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 not we cast him out? And he said unto them, This kind can come forth by nothing, but by prayer and fasting.
Notice, the disciples should have been able to cast him out, what was wrong? For years in various Pentecostal circles when somebody needing deliverance did not get set free it always seemed to be explained by saying that some devils are too strong and would require days and weeks of prayer and fasting in hopes that the one ministering deliverance would finally have enough power to cast out such powerful demons.
I'd like to look at these scriptures from another angle. Did you notice what the father of the child asked Jesus? In verse 22, he said to Jesus, "but if thou canst do anything, have compassion on us, and help us." It was obviously, in light of all the scriptures we've read thus far, widely known just what would happen if Jesus would have compassion on someone. Things happen when Jesus feels compassion and if we will operate in that same compassion in our homes, ministries, work place, community, and for sure, in our churches, the term miraculous would be a weak description of what would occur!
The disciples got Jesus off to the side in private where they could really pour the pressure on and asked him why they couldn't cast the demon out of the child and Jesus said, "this kind can come forth by nothing but by prayer and fasting". What (?) can come forth by nothing, but by prayer and fasting? Compassion!
The man didn't just approach Jesus and insist on healing the child but he first and foremost asked that Jesus would have compassion on the child and help him. When compassion gets involved, we'll do anything we can and take as long as we need too, to see deliverance manifested. So we could say, the kind of compassion needed for such drastic and critical cases can come forth by nothing but by prayer and fasting. This will crucify the flesh which doesn't normally want the inconvenience of being bothered by such. However, the greater miracles, signs, and wonders, of the end-times will come about as a result of those who do want the real, genuine, most effective tools for supernatural ministry and that will require prayer and fasting, crucifying self, and being a vessel that is moved with His compassion. If you are willing to do it God's way, it could just as easily be you through which God moves so mightily as anyone. God doesn't have favorites and unlike many religious leaders today, God isn't star-struck! I can promise you that if I am full of self, I won't have the kind of compassion needed for this end-time ministry, and neither will you. If I am full of my ministry, and what I do, and who I know, and I want to go around dropping names, I might be popular but I won't be able to help you! You need someone that can be moved with compassion and help you and there's One who can, who will help you, any day, any hour, any place, or any circumstance, and His Name is Jesus!
Prayer and fasting gives me the openness and the know-how of how to open myself so that his compassion, the kind of compassion that will help a man whose little boy is being thrown here and there and devils are tearing him and tormenting him and trying to kill him. There is compassion to be felt and experienced by the Spirit to you this very moment. It comes because Jesus wants to reach out and touch you, but this kind of compassion cannot come forth unless you are willing to pray and fast. You'll experience it, but if you want to walk in it, if you want it to come and be there for you in the future, or for those you love, you are going to have to sell out, pray and fast, and yield yourself, and dedicate yourself totally to Jesus so that his compassion will come forth in you because it will heal every sickness and disease. It'll reach out and raise dead people. It'll open and restore deaf and dumb children. It'll open blind eyes and once they can see, they will follow Jesus.