Matthew 21:18-22, Mark 11:12-14, Mark 11:20-24.
Jesus found a fig tree on the way to Jerusalem from Bethany. He noticed there were no fruit on that tree. He cursed the tree saying "May you never bear fruit again." Immediately the tree withered. Disciples were amazed by watching this. Jesus said to them "I tell you the truth, if you have faith and do not doubt, not only can you do what was done to the fig tree, but also you can say to this mountain, 'Go, throw yourself into the sea,' and it will be done. If you believe, you will receive whatever you ask for in prayer.".
This is a rather difficult part to understand. Jesus cursed a fig tree and killed it...? It seems this was implying the destiny of Jerusalem which did not bear fruit.
Reference:Faith of a mustard seed
