New International Version
19 Then the disciples came to Jesus in private and asked, “Why couldn’t we drive it out?”
20 He replied, “Because you have so little faith. Truly I tell you, if you have faith(A) as small as a mustard seed,(B) you can say to this mountain, ‘Move from here to there,’ and it will move.(C) Nothing will be impossible for you.”  [a]
- Matthew 17:21 Some manuscripts include here words similar to Mark 9:29.