Matthew 21:18-27

18 In the morning, as he was returning to the city, he became hungry. 19 And seeing a fig tree by the wayside, he went to it and found nothing on it but only leaves. And he said to it, “May no fruit ever come from you again!” And the fig tree withered at once. 20 When the disciples saw it, they marveled, saying, “How did the fig tree wither at once?” 21 And Jesus answered them, “Truly, I say to you, if you have faith and do not doubt, you will not only do what has been done to the fig tree, but even if you say to this mountain, ‘Be taken up and thrown into the sea,’ it will happen. 22 And whatever you ask in prayer, you will receive, if you have faith.”

23 And when he entered the temple, the chief priests and the elders of the people came up to him as he was teaching, and said, “By what authority are you doing these things, and who gave you this authority?” 24 Jesus answered them, “I also will ask you one question, and if you tell me the answer, then I also will tell you by what authority I do these things. 25 The baptism of John, from where did it come? From heaven or from man?” And they discussed it among themselves, saying, “If we say, ‘From heaven,’ he will say to us, ‘Why then did you not believe him?’ 26 But if we say, ‘From man,’ we are afraid of the crowd, for they all hold that John was a prophet.” 27 So they answered Jesus, “We do not know.” And he said to them, “Neither will I tell you by what authority I do these things.

A fruitless fig tree was an Old Testament symbol of God's judgment on Israel's idolatry and corruption. For example:

“‘I will take away their harvest,
declares the Lord.
There will be no grapes on the vine.
There will be no figs on the tree,
and their leaves will wither.
What I have given them
will be taken from them.'” [Jeremiah 8:13, NIV]

So, the episode with the cursed fig tree is a living parable Jesus is acting out in front of the disciples. He is showing them the consequences for the hard-heartedness of the religious leaders, namely that the Temple will soon be destroyed.

At the time Jesus is speaking the Temple and its leadership would have seemed permanent and unassailable. And yet within a generation (in AD 70) the entire thing would be overthrown as a consequence of Israel’s rejection of Jesus. (Look at the leadership’s dishonesty in verses 23-27.) Jesus wants his disciples to have faith that God hears their prayers and can do the seemingly impossible.