Mark 11:23
For verily I say unto you, That whosoever shall say unto this mountain, Be thou removed, and be thou cast into the sea; and shall not doubt in his heart, but shall believe that those things which he saith shall come to pass; he shall have whatsoever he saith.
The mountain to be commanded to be removed and cast into the sea is mountains of difficulty standing against the proclamation of the truth, and those mountains are removed through God's wonderful providence as the gospel work advances. Through the overruling work of divine Providence those great difficulties in proclaiming the truth will be taken away, so that the message can go forward until the whole earth has been warned.
Their removal and casting into the sea prepares the way of the Lord for the spread of the gospel in its purity under the overruling guidance of the Holy Spirit. Then the stream of living water will deepen and widen in its course, in all fields nigh and afar off. This comes as men are called from the plow and from the more common commercial business vocations that largely occupy the mind, and are educated in connection with men who have had experience, men who understand the truth.
It is Omnipotence Himself who speaks to those mountains of difficulty and clears them out of the way for the spread of the gospel in its purity. This clearing comes when workers of divine appointment turn away from human understanding and fables, and when those once in evangelistic work but drawn into restaurants, food stores, and other commercial lines return to diligent Bible study. They are to study the Bible diligently, hold forth the Word of God, and give the people rich Bible food with the Word in hand, in cooperation with heavenly angels. Then hindrances are swept aside, so the message for earth's dwellers is seen and heard and understood, people know what is truth, the marked workings of Providence are seen and recognized, and the work moves onward and still onward to victory.
The uprooting of a mountain and casting it into the sea is a work no human power could do, any more than human power could change one precept of God's law or erase a promise to those who obey Him.
The verse also calls for faith in God in asking for healing when sick. The sick person is to ask for himself in faith, and others are to keep his case before the Lord in public prayer and in private prayer. The prayer is that the great Physician will stay the course of disease, spare life, and make well. All such believing prayer is offered on condition that it is the Lord's will, in accordance with His holy will, and for the glory of God.