13:6-9 What does this parable teach?

This is called the parable of the barren fig tree. It illustrates the fruitlessness of Israel (cp Isa 5:1-7). Jesus told the parable of the barren fig tree to enforce His declaration in Lk 13:1-5 that unless the Jews repented they would all perish (cp Lk 13:1-5).

In the context of the calamities that overtook the Galileans and those on whom the tower of Siloam fell, Jesus teaches in the parable that God's patience eventuates in judgement if sinners do not repent. The owner of the vineyard is a figure of God, and the vinedresser, Jesus.

The parable also teaches that just as the vinedresser was only prepared to give the tree another year to bear fruit, so too Jesus will not plead for sinners any longer once the day of grace has passed. But this is not only a warning to a fruitless nation or a fruitless sinner, it is also a warning to a fruitless church or a fruitless believer (cp Mt 3:7-10; 7:15-27; Lk 8:5-9, 11-15; Jn 15:1-6, 16; He 2:2-3).

The barren fig tree in the parable should not be confused with the fig tree Jesus cursed in Mt 21:17-22 or Mk 11:12-14, 20-24. The lesson we learn from Jesus cursing that fig tree is a divine object lesson in faith. It is not about the fruitlessness of Israel (cp Mt 21:17-22).