Rabanus Maurus
Catena Aurea · Matthäusevangelium 21
And he left them, and went out of the city into Bethany; and he lodged there. Now in the morning as he returned into the city, he hungered. And when he saw a fig tree in the way, he came to it, and found nothing thereon, but leaves only, and said unto it, Let no fruit grow on thee henceforward for ever. And presently the fig tree withered away. And when the disciples saw it, they marvelled, saying, How soon is the fig tree withered away! 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. And all things, whatsoever ye shall ask in prayer believing, ye shall receive.
But whenever we are not heard when we pray, it is either because we ask something adverse to the means of our salvation; or because the perverseness of those for whom we ask hinders its being granted to them; or because the performance of our request is put off to a future time, that our desires may wax stronger, and so may have more perfect capacity for the joys they seek after.