Jesus had just cursed the fig tree. Although it looked a healthy tree, it was without fruit and therefore useless. The words of Jesus to the tree, saying that it would never bear fruit again, instantly removed the fig tree's purpose, and even its bright leaves withered instantly. It was dead.
 
This was an acted parable. Israel had been the outward display of God's purpose for the world, but had become useless because they had stopped trusting God. Instead, they trusted the mechanics of their religion and their leaders enjoyed the power structure which kept them respected as authority figures. Instead of being a vehicle of God's saving grace to the world, Israel had become an obstacle to God's purpose instead: it could no longer be trusted to show God's love and mercy to the world.
 
The Word of Jesus was effective in dealing with the fig tree, and likewise Israel would also be destroyed by His Word (Matthew 24:1-2). 40 years after Jesus became the Passover Lamb, the city was destroyed along with the sacred temple; and since then, no sacrifices for sins have ever been made in Jerusalem. When the disciples questioned why the curse had been so effective, Jesus said that if they understood and trusted God's will, they could also speak out in faith and God would remove other mountain-like obstacles to His Kingdom (Acts 5:1-11).
 
These verses encourage us to stay close to the Lord, so that we will understand His Word and share a passion for His purposes. To speak or pray in faith is not a matter of 'generating the feelings of faith', but knowing from the Lord what His will is and simply announcing it as Peter did in Acts 3:6, and Paul did in Acts 20:22-24. Faith is not hoping that what we want might happen, but knowing that God's purpose will certainly happen. The prayer or announcement places faith on record so it is clear that what happens is no accident, but God's sovereign will.