Mountains are symbolic of kingdoms, governments or obstacles/problems to name a few. Let’s look at the context and see what has been happening. Yeshua came into the city of Jerusalem and overturned the money-changer tables and rebuked the religious leaders and their teachings and oral traditions. The next day he was hungry and went over to a fig tree and found no fruit, even though it was early for fruit. So, he cursed the tree and said that no one would eat fruit from it again. The tree was symbolic of Israel and it was not producing the fruit it should have and it was going to be “cursed” and dispersed into all the nations (the sea of humanity) very soon. The next day they were coming to Jerusalem again and the Apostles noticed that the tree had withered and they were amazed. Yeshua then tells them to have faith in God and that whoever says to “this” ( a particular one) mountain to be removed and cast into the sea, and does not doubt, it shall be granted him. But what is he talking about. Yeshua is talking about what he has been experiencing, unbelief among the “fig tree” (Israel) and no fruit. When he says “this mountain” he is referring to Mount Moriah where the Temple was and the governing body of the people (Sanhedrin) met. False teachings and all sorts of corruption were coming from there and they were corrupting the people. False doctrine is an obstacle (mountain) but if you have emunah (faith) in God, all of that can be overcome. He was also alluding to the fact that Jerusalem/Temple would be destroyed and “cast into the sea” because it was not producing the true teachings required. Casting a mountain into the sea has been used in the Scriptures to describe coming judgment (Psa 46.2; Rev 8.8). Judgment was coming because the false teachers were keeping the people away from the Kingdom of God with their teachings. So, not only is Yeshua saying that there will be a historical fulfillment of this verse in the coming judgment if the people don’t repent, but he is also saying that if they have faith in God, the falsehood of the teachings they have been hearing can be overcome and they can enter the Kingdom of God in a spiritual sense. This verse, interestingly enough, has been misinterpreted by many in the so-called “faith movement” to mean that if we say anything, and have faith in God and not doubt, then we can have whatever we say. Of course this is nonsense but people still believe it. This verse is saying quite the opposite. Any false teaching or obstacle that gets in the way of the truth can be uprooted and removed with faith in God.