Mark 9:28 Commentary and Bible Study

The disciples had previously been given this power by Christ, and they had successfully exercised it in the villages and the towns where, like Christ himself, they had been healing people and casting out demons. So why could they not do it here? Were those powers that they had been given, only temporary, for their mission, or did they simply fail in this case? The narrative implies that they failed, because when they ask the Lord, ‘Why could not we cast him out?’, the reply of the Lord was that this sort, this kind, only comes out by prayer and fasting. Matthew adds a further explanation for their failure: it was ‘because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you’ (Matthew 17:20). The person who is going to heal this boy has got to be very serious and very intently engaged in prayer for him. That is the only way this can be done. Here is an obdurate and a difficult case. But the fundamental problem was their unbelief. Faith lays hold of all the power of God. The power of God can immediately accomplish anything he pleases. If the mountain is moved it is the power of God that moves it, but faith takes hold of that power. By prayer we call on the power of God to help us, according to his will. By fasting we focus our thoughts on God and show him our earnestness. We discipline ourselves with fasting to concentrate our prayers on some great need that we wish to bring before him. Wonderfully, Christ says that by doing so, we can overcome all the power of the enemy, and ‘the God of peace shall bruise Satan under your feet shortly’ (Romans 16:20).