NOTES for Mar 11:23
Jesus does not ask us of course to cast mountains into the sea. In fact, if we really have faith in God, that is trust in God Who created seas and mountains, then we will not dare to remove mountains He created! If that is the case, what is He talking about then?
Jesus uses this description of "mountain cast into the sea" above all as an image of what is absolutely impossible to be made by human strengths, but possible to be made by God. Therefore, Jesus speaks one more time about a genuine faith - "evidence of things not seen” (Heb.11 1), binding Man to God in such way that miracles begin to occur in that man’s life - the manifestations of the actions of God’s power.
Doubt opposes such a faith; this doubt can be very simple: but can God do what I ask Him? Such a doubt is certainly easier to surmount. But there are more delicate doubts; for example: is God listening to my prayer? We need here an internal image of God, not only an Almighty God, but also a loving God. Here is an even more complicated example: do I have enough faith in order that what I ask gets realized? Such doubt is an entrance to the vicious circle, making us to be self contained, separating us from God. We can destroy it only by a resolute effort – reject egocentric thoughts and turn to God; but this is too difficult for us, harden by our egoism.