Look at the events:

• Jesus cursed the fig tree that had no fruit
• They go to Jerusalem
• Entered temple
• Jesus drove out the merchants
• Scathing rebuke by Jesus directed at leadership
• Leaders begin hatching plan to destroy Jesus
• Disciples see fig tree withered and ask Jesus about it
• He speaks of casting “this mountain” into the sea.

Something tells me that their thoughts were not on a physical mountain. Instead, Jesus tied the incident regarding the fig tree together with asking for anything in faith, and then specifically spoke of asking that this mountain be cast into the sea. If the disciples wanted to express their doubts about the moving of an actual mountain, I think they would have, either by asking Jesus about it or more likely in private, when they were on their own. As it is, they would have been feeling the impact of everything that was happening at the time. I’m sure they enjoyed some of the interplay between Jesus and the leaders of Jerusalem, but they also knew how dangerous it was. We know this from the record because it reveals them being fairly freaked out.

I think they were feeling the weight of the mountain while they were in Jerusalem that day, and I am certain they carried the sense of back with them to the fig tree. Regarding their understanding of the figurative use of mountains, especially Jesus’ relation to it, consider the following:

He was in the world, and the world was made through Him, and the world did not know Him. He came to His own, and those who were His own did not receive Him. John 1:10-11 NASB

This reality was playing itself out in front of them through that whole experience.

“O Jerusalem, Jerusalem, the city that kills the prophets and stones those sent to her! How often I wanted to gather your children together, just as a hen gathers her brood under her wings, and you would not have it! “Behold, your house is left to you desolate; and I say to you, you will not see Me until the time comes when you say, ‘BLESSED IS HE WHO COMES IN THE NAME OF THE LORD!’” Luke 13:34-35 NASB

Jesus addressed Jerusalem as representative of his own who did not receive him.

Tell me, you who want to be under law, do you not listen to the law? For it is written that Abraham had two sons, one by the bondwoman and one by the free woman. But the son by the bondwoman was born according to the flesh, and the son by the free woman through the promise. This is allegorically speaking, for these women are two covenants: one proceeding from Mount Sinai bearing children who are to be slaves; she is Hagar. Now this Hagar is Mount Sinai in Arabia and corresponds to the present Jerusalem, for she is in slavery with her children. But the Jerusalem above is free; she is our mother. Galatians 4:21-26 NASB

Years later, Paul would also make an even more pointed description of the mountain that Jesus came to set his own free from. The present Jerusalem corresponds to Mount Sinai, the place where the Law was given.

For you have not come to a mountain that can be touched and to a blazing fire, and to darkness and gloom and whirlwind, and to the blast of a trumpet and the sound of words which sound was such that those who heard begged that no further word be spoken to them. For they could not bear the command, “IF EVEN A BEAST TOUCHES THE MOUNTAIN, IT WILL BE STONED.” And so terrible was the sight, that Moses said, “I AM FULL OF FEAR and trembling.” But you have come to Mount Zion and to the city of the living God, the heavenly Jerusalem, and to myriads of angels, to the general assembly and church of the firstborn who are enrolled in heaven, and to God, the Judge of all, and to the spirits of the righteous made perfect, and to Jesus, the mediator of a new covenant, and to the sprinkled blood, which speaks better than the blood of Abel. Hebrews 12:18-24 NASB