Luke chapter 13

5 I tell you, no! But unless you repent, you too will all perish.

6 Then he told this parable: A man had a fig-tree, planted in his vineyard, and he went to look for fruit on it, but did not find any.

What attracted me here is the word "Then", which connected the former teaching of repentance and the later parable of unfruitful fig-tree. Jesus used unfruitfulness as a complement to explain the repentance. So that we can understand the relationship between yielding fruit and the repentance. Compared with the unfruitful fig-tree which is going to perish due to its unfruitfullness,  yielding fruit is just the manifestation of true repentance. 

Let's recall what John the Baptist has taught:

Produce fruit in keeping with repentance. (Luke 3.8)

That's the point. Our repentance should not be represented in a psychological or an oral way, but rather in our behaviors. If we do not have matched behaviors, he said:

The axe is already at the root of the trees, and every tree that does not produce good fruit will be cut down and thrown into the fire. (Luke 3.9)

It's the same parable with Jesus's. If we could not yield fruits of Holy Spirit, our repentance might be not that true, and we would be cut as well.

Another thinking is about the role of the guard of vineyard:

 7 So 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 round it and fertilise it. 

The guard interceded with the master for the surival of the fig-tree, with his promise of care and planting. It reminds us that the faith of our church members are really the responsibility of all of us. We all are both trees which must yielding fruits and the guards of God's vineyard who should take care of trees. We should always (but not till the moment of any tree's perishing) pray for each other and plant each other with our every effort.