Because of your unbelief. — The various reading, “Because of your little faith,” found in many, but not the most authoritative MSS., is interesting as an example of a tendency to tone down the apparent severity of our Lord’s words. They show conclusively that the disciples themselves came under the range of His rebuke to the “faithless and perverse generation.”
If ye have faith as a grain of mustard seed. — The hyperbolical form of our Lord’s words, repeated afterwards in Matthew 21:21, excluded from the thoughts of the disciples, as from our own, the possibility of a literal interpretation. The “grain of mustard seed” was, as in Matthew 13:31, the proverbial type of the infinitely little. To “remove mountains” was, as we see in 1 Corinthians 13:2 (this may, however, have been an echo of our Lord’s teaching), the proverbial type of overcoming difficulties that seemed insurmountable. The words were, we may believe, dramatised by a gesture pointing to the mountain from which our Lord and the three disciples had descended, as afterwards by a like act in reference to the Mount of Olives (Matthew 21:21).
Nothing shall be impossible unto you. — The words, absolute as they sound, are yet, ipso facto, conditional. Nothing that comes within the range of faith in the wisdom and love of God, and therefore of submission to His will, is beyond the range of prayer.