William Burkitt on Mark 11:20

The blasting and sudden withering of the fig-tree at the word of Christ, plainly shewed his divine power, and by this miraculous operation, our Saviour designed to shew his disciples the mighty power of faith; that is, a full persuasion of the power of God, that he is able, and of the goodness of God, that he is willing, to grant whatever we ask according to his will, that has a tendency to his glory and our good.

Learn hence, That faith is a necessary and principal ingredient in prayer praying without faith, is like to a man's shooting without a bullet; it makes a noise, but doth no execution.

Secondly, That whatsoever good thing God had made the matter of his promise, shall be given to good men in a way of perfromance, provided they pray in faith. Whatsoever ye desire, believe that ye receive them, and ye shall have them.