v21. Jesus answered and said unto them, Verily I say unto you, If ye have faith, and doubt not, ye shall not only do this which is done to the fig tree, but also if ye shall say unto this mountain, Be thou removed, and be thou cast into the sea; it shall be done.
v22. And all things, whatsoever ye shall ask in prayer, believing, ye shall receive.
Jesus had just cursed a fig tree to withered away, and as soon as our Savior had cursed it, it began to wither. In the book of Mark, we were told that the next morning Peter says, Master, behold, the fig tree which thou cursedst is withered away (Mark 11:20).
Matthew saith, when the disciples saw it, they marveled, saying, how soon the fig tree is withered away. Upon this our Savior told Peter and the rest, that if they had faith, and doubted not, they should not only do that which he had done to the fig tree, but if they said to that mountain, Be removed and cast into the sea, it should be done.
All things, whatsoever ye shall ask in prayer believing, ye shall receive. It is an expression which ought not to be strained further than to signify, that there is nothing conducive to the glory of God and our own good, than for believers to receive at the hand of God, if they can believe without doubting that what they would have shall come to pass.
But there were of old special promises, not made to the people of God in general, but to particular persons, for particular ends; we cannot expect to do or obtain such things now. Nothing is too big for true faith to obtain, but that faith must have a promise to lean upon, and it must be showed by prayer, as Matthew 21:22.
That it must be also attended with charity, a charitable heart, ready to forgive, and actually forgiving, our brethren their trespasses. And all things whatsoever, not only miracles, but any other thing which may be for the honor of God, the interest of religion, the spreading of the Gospel, the enlargement of the kingdom of Jesus Christ, their own spiritual good, and the welfare of immortal souls.
Ye shall ask in prayer, believing. Ye shall receive of God, through Christ, freely and fully, and shall have and enjoy them, either they themselves or for those they have asked. Jesus wants us to pray and keep the faith, so that we can received.