Matthew 17:19-20

"Then the disciples came to Jesus privately and said, "Why could we not drive it out?". And He said to them, "Because of the littleness of your faith; for truly I say to you, if you have faith the size of a mustard seed, you will say to this mountain, 'Move from here to there,' and it will move; and nothing will be impossible to you".

“I look at the disciples and they were men of faith before the Cross but one day they stepped out to pray for a boy with a demon and they couldn't get the demon out. Jesus came and cast it out proving it was the will of God to get that demon out. Today if we try to get someone healed and they don't, we say it wasn't the will of God to heal that person. The disciples were shocked and asked why couldn't we cast that demon out? Why were they shocked? Because they had some success before in casting demons out but then they hit a disappointment.

But Jesus said; "This type only come out by prayer and fasting". He DID NOT mean this type of demon only comes out by prayer and fasting. Every demon has lost authority and must come out in the Name of Jesus. There is no hierarchy of demon that can resist you unless you have fasted and prayed. If you believe that lie, every demon will tell you; "I am the kind that only come out by prayer and fasting and you haven't fasted". So you wait for a week fasting and in that time the demon kills the person. Jesus was saying this kind of unbelief comes out by prayer and fasting. You can have faith to cast out demons but if you have disappointment that will hinder your faith”.

Ref: Rob Rufus - "Invading the Impossible – Part 5" - City Church International, Hong Kong - 17th February 2008.