6Then [Jesus] told this parable: "A man had a fig tree growing in his vineyard, and he went to look for fruit on it but did not find any. 7So he said to the man who took care of the vineyard, 'For three years now I've been coming to look for fruit on this fig tree and haven't found any. Cut it down! Why should it use up the soil?' 8'Sir,' the man replied, 'leave it alone for one more year, and I'll dig around it and fertilize it. 9If it bears fruit next year, fine! If not, then cut it down.'" (NIV)
Chapter 13 begins with people raising to Jesus a concern regarding some Jews who were killed by Pilate. It seems they are asking Jesus to give some explanation of their personal behavior that should justify their executions. Recall, the Jewish culture in which this is taking place is heavily legalistic in their world view, thus by asking Jesus about the execution they are seeking validation of that view from Jesus. Jesus responds with a rhetorical question, asking the crowd if these particular Jews were worse sinners than others in the area. Answering His own question, we discover that they were not worse than the others. Jesus continues by considering another group of people who were killed apparently in a random accident when a tower fell. Again, Jesus states these Jews were in fact no worse than the any others in Jerusalem at the time.
Then Jesus tells the parable of the Barren Fig Tree: It tells of the owner of a vineyard who finds a fig tree of his not bearing fruit. The owner decides to cut it down, as is his right, and orders the care taker to do just that. The caretaker, however, advocates for the fig tree and says he personally will nurture it and see if the behavior changes, only then should it be cut down.
Here the vineyard owner represents God the Father, and the fig tree, us people, or more specifically the Jews talking to Jesus. The barren nature of the tree is symbolic of us failing to fulfill God's Law and thus being justifiably liable for punishment. Meaning, us people are in fact deserving of death, that is to be cut down like the fig tree, for the types of lives we are living. The vineyard caretaker, Jesus the Son, steps in on our behalf saving us from the just punishment dealt out by the Father for our behavior. He advocates for us, just as with the tree, without any sign or effort on our behalf, an analogy for how Grace works for us personally with respect to the death penalty we face for our sin.
What Jesus is actually saying to his Jewish audience is they are fundamentally mistaken in their assumptions about the situation. More broadly, they are mistaken in thinking there are any Jews not deserving death for the lives they are living. It is not with an explanation of why these particular Jews have been killed by Pilate they should be concerned. Rather, given they all themselves have failed to fulfill God's law and are facing death, they should be concerned and interested in why everyone has not been killed as Justice demands. Jesus says, jumping back to verse 5, they should all ask for forgiveness from God (i.e. receive Grace) or they too will face their just deaths.
As a final thought, I'm left wondering if in fact, "next year" will be treated any differently by either the owner or caretaker.