The disciples' question, "Why could we not cast [the demon] out?" suggests that they could not see any reason for their failure. Jesus replies emphatically, "Because of your unbelief. . . . [T]his kind does not go out except by prayer and fasting" (Matthew 17:20-21). Here He emphasizes the necessity and power of faith, as well as the need of intercession and self-denial. Their great lack of faith was not a lack of intellectual acceptance of all Christ stood for, but the lack of living faith in His divine omnipotence. He taught with excellence and performed many miracles, yet His teaching and miracle-working made little progress in the people's faith. Unbelief still dominated them (Romans 3:3-4).

However, Christ continued in patience to teach the people and to work mighty miracles for them. Thankfully, our Savior is patient in dealing with our sluggishness and dullness in learning God's truth and faithfully living His way of life.