Where a man brings his son to Jesus, after the disciples fail to cast out a demon that has been tormenting the boy to near death. If you study it earnestly, there is some bit of chaos in the scene especially if you read from Mark 9:14-29 (a more vivid view)
However there is something crucial Jesus hints on but many of us miss it while reading. If you look in Mark 9:19 NKJV
“He answered him and said,”O faithless generation, how long shall I be with you?…”
Then later in Mark 9:29 when the disciples asked Him; why couldn’t they cast the demon out of the boy? He answers them with the most unexpected reply.
“So He said to them, “This kind can come out by nothing but prayer and fasting.”
So that’s what we have to do? Am sure they must have thought to themselves too. But that’s far from the truth. Was Jesus trying to say fasting and prayer will cast out the demon or their faith will cast out the demon?
Look at Matthew 17:20-21
“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. “
Jesus strait charges them, ‘because of your unbelief.’ Their lack of faith made the demon fail to get out. That only means one thing, demons know how to sense faith, if they see it, they move out. It’s automatic.
There is no measure of faith however, it’s quite clear up there, even as small as a mustard seed is enough to make a mountain move. Notice something else here; he tells them to do something to grow their faith in the next verse, 21.
“However, this kind does not go out except by prayer and fasting.”
This kind of unbelief; only goes out by prayer and fasting. It was never about the demon as most of us perceive it, it was about taking out the lack of faith. We fast and pray to grow in faith. Then this faith overcomes the world and we are transformed.
God can only be pleased through your faith in Him,nothing else. Then your faith in Him causes Him to move and manifest His power and word in your life.
Don’t think that doing all those acts of righteousness, abstaining from sin will fully please God as much as your faith in Him, no.
If you can let go of the plans you have for yourself and surrender to Him. Let Him show you His plans for your life. That is the ultimate way to win by faith, right there. Following His blueprint instead of yours is what will cast out those devils from your life, even those problems that have lingered for years will disappear.

If you let go of your current situation, and look up to Him. That’s all you have to do. Then follow His ways and live according to His word(you will be acting on faith) There you will meet Him and see His glory with your bare eyes.