Jesus answered. To the apostles' question the Lord makes reply, drawing a lesson, not such as we should have expected, but one of quite a different nature, yet one which was naturally deduced from the transaction which had excited such astonishment.
They marvelled at this incident; let them have and exercise faith. and they should do greater things than this. Christ had already made a similar answer after the cure of the demoniac boy (Matthew 17:20, where see note).
If ye have faith, and doubt not ( μη Ì διακριθῆτε). The whole phrase expresses the perfection of the grace. The latter verb means "to discriminate," to see a difference in things, hence to debate in one's mind.
The Vulgate gives, Si habueritis fidem, et non haesitaveritis. What is here enjoined is that temper of mind which does not stop hesitatingly to consider whether a thing can be done or not, but believes that all is possible—that one can do all things through Christ who strengthens him.
So the apostles are assured by Christ that they should not only be able to wither a tree with a word, but should accomplish far more difficult undertakings. This which is done to the fig tree ( το Ì τῆς συκῆς); as, "what was befallen to them that were possessed with devils ( τα Ìτῶν δαιμονιζομε ìνων)" (Matthew 8:33).
The promise may intimate that it was to be through the preaching of the apostles, and the Jews' rejection of the salvation offered by them, that the judgment should fall on the chosen people. Thus they would do what was done to the fig tree.
And in the following words we may see a prophecy of the destruction of the mountain of paganism. Or it may mean that theocratic Judaism must be cast into the sea of nations before the Church of Christ should reach its full development (Lange).
This mountain. As he speaks, he points to the Mount of Olivet, on which they were standing, or to Moriah crowned by the glorious temple. Be thou removed; be thou taken up; ἀ ìρθητι, not the same word as in Matthew 17:20.
The sea. The Mediterranean (see a similar promise, Luke 17:6). It shall be done. It was not likely that any such material miracle would literally be needed, and no one would ever pray for such a sign; but the expression is hyperbolically used to denote the performance of things most difficult and apparently impossible (see Zechariah 4:7; 1 Corinthians 13:2).