Increase our faith
The circumstances surrounding the miracle
The conversation with the father
Having previously been able to exorcise demons (6:13), the disciples assumed they could do so whenever they wished. They failed, however, because of their lack of faith. Spiritual power is not something which once possessed will always be available. It must be maintained and renewed. Disciples then and now must constantly learn and relearn this lesson
Apparently they had trusted in past successes (cf. 6:7, 13) and had failed.
This episode of desperate human need and the disciples’ failure contrasts sharply with the glory of the transfiguration. It shows the reality of living in the world in the absence of Jesus.
O unbelieving generation emphasizes the characteristic cause of all spiritual failure—lack of faith in God
Jesus took up the father’s words of doubt, If You can, to show that the point was not His ability to heal the boy but the father’s ability to trust in God who can do what is humanly impossible
Jesus had given His disciples authority to cast out demons (Mark 6:7, 13), and yet their ministry to the boy was ineffective. No wonder the Lord was grieved with them! How often He must be grieved with us when we fail to use the spiritual resources He has graciously given to His people!
The main lesson of this miracle is the power of faith to overcome the enemy (Mark 9:19, 23–24; and see Matt. 17:20). Why had the nine disciples failed? Because they had been careless in their personal spiritual walk and had neglected prayer and fasting (Mark 9:29). The authority that Jesus had given them was effective only if exercised by faith, but faith must be cultivated through spiritual discipline and devotion. It may be that the absence of their Lord, or His taking the three disciples with Him and leaving them behind, had dampened their spiritual fervor and diminished their faith. Not only did their failure embarrass them, but it also robbed the Lord of glory and gave the enemy opportunity to criticize. It is our faith in Him that glorifies God (Rom. 4:20).