Why did Jesus curse the fig tree? “And on the morrow, when they had come out of Bethany, he [Jesus]
  hungered. And seeing a fig tree afar off having leaves, he came, if
  perhaps he might find anything thereon: and when he came to it, he
  found nothing but leaves; for it was not the season of figs. And he
  answered and said unto it, ‘No man [will] eat fruit from you from now
  on — for ever.’ And his disciples heard it. Mark 11:12-14


Several pastors interpret this event mentioned in Mark 11:12-14, as God will abolish those who do not yield like this fig tree. However, on the way back when the disciples saw the fig tree   withered away from the roots, Jesus uses this incident to explain faith. 

Why did Jesus cursed the tree, when it was not the time or season to bear fruits?


  22 “Have faith in God,” Jesus answered. 23 “Truly[f] I tell you, if
  anyone says to this mountain, ‘Go, throw yourself into the sea,’ and
  does not doubt in their heart but believes that what they say will
  happen, it will be done for them. 24 Therefore I tell you, whatever
  you ask for in prayer, believe that you have received it, and it will
  be yours.


If Jesus used this incident to explain faith why do preachers use this incident to explain it as a warning to the sinners who didn't turn back to our Lord like this unyielding fig tree?
“From the fig tree learn its lesson: as soon as its branch becomes tender and puts out its leaves, you know that summer is near. 33 So also, when you see all these things, you know that he is near, at the very gates. 34  Truly, I say to you, this generation will not pass away until all these things take place. 35  Heaven and earth will pass away, but my words will not pass away. (Matthew 23:32-35)


The miracle of the cursing of the fig tree has a literary form called an inclusio, or what many seminary students have come to affectionately know as "the sandwich."  The idea is that two stories (Story A and Story B) are related, and the way the hearer is cued to know that fact is the arrangement.  In an inclusio, Story A is started, but not finished. Story B then comes in the middle. Finally, there is a return to Story A. The point of the inclusio is always story B, where Story A is usually the frame. 

In the Synoptics, the story of the fig tree has as its inclusio Jesus clearing the Temple.

The Fig Tree is a metaphor for a vibrant, living thing that is supposed to be giving life. Like the tree in Psalm 1, the man who does not walk in the way of the wicked is:


  ...like a tree planted by streams of water, 
     which yields its fruit in season 
  and whose leaf does not wither— 
     whatever they do prospers.


Unlike a tree, however, a man's 'season' is his lifetime. And, the Temple (having been recently reconstructed) should also be in its season at all time.

The fact that Jesus finds a barren tree is disconcerting, especially since he, the Messiah has come. Like his parable of the bridesmaids (where 5 foolish women burn all their oil but 5 wise ones save it), Jesus expects his people his people to be ready.  (Indeed, there are several parables that teach this very point). Upon finding his Temple in disarray, Jesus is visibly disappointed that the fruits of Temple worshippers are noticeably absent. Like the Tree, the Temple worshippers may not have thought they needed to be in season, but they are wrong.  

As Paul later would admonish Timothy, Jesus' followers must be "be ready in season, out of season."

In order to be ready like that, however, one must have complete faith that the Lord is coming. As Jesus says


  if the master of the house had known in what part of the night the thief was coming, he would have stayed awake and would not have let his house be broken into. Therefore you also must be ready, for the Son of Man is coming at an hour you do not expect.


The sin of those in the Temple was simply that they were not ready. Those in the Temple should have been bearing fruit, not selling it. Though their own scriptures had been saying that the Messiah would be returning for centuries, when it actually happened, people were clearly not ready.  Even the Temple had no special sway - people treated it like a shopping mall rather than the house of God. People were not "bearing fruit in keeping with repentence." 

It was as Peter would say:


  The Lord is not slow in keeping his promise, as some understand slowness. He is patient with you, not wanting anyone to perish, but everyone to come to repentance.


As people awaiting the return of the Lord again, the lesson we are to take is that we should be producing fruit at all time. If our hope is to wait to be fruitful until the 11th hour, we better pray Jesus doesn't come at 10:30.