Matthew 17:14-20
14 When they came to the crowd, a man came to him, knelt before him, 15 and said, “Lord, have mercy on my son, for he is an epileptic and he suffers terribly; he often falls into the fire and often into the water. 16 And I brought him to your disciples, but they could not cure him.” 17 Jesus answered, “You faithless and perverse generation, how much longer must I be with you? How much longer must I put up with you? Bring him here to me.” 18 And Jesus rebuked the demon, and it came out of him, and the boy was cured instantly. 19 Then the disciples came to Jesus privately and said, “Why could we not cast it out?” 20 He said to them, “Because of your little faith. For truly I tell 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 for you.”
From the New Revised Standard Version. Reprinted with permission from HarperBibles.