In most study bibles, commentaries, and preaching, the parable of the barren fig tree usually receives little attention or is skipped over entirely. Many study bible notes point out something entirely unhelpful such as, "The unproductive tree represents people who were not producing fruit." Super helpful, right? Not exactly. Of course that is what the tree represents, but who and why? As usual, the fathers are helpful. In the early church, the tree was viewed as Israel or, more broadly, humanity as a whole. If viewed as Israel, the three years were generally interpreted to be the three years of Jesus' earthly ministry. If fallen humanity is in view, the three years were understood more allegorically. Taking the latter view, St. Augustine writes, "This tree is the human race. The Lord visited this tree in the time of the patriarchs, as if for the first year. He visited it in the time of the law and the prophets, as if for the second year. Here we are now; with the gospel the third year has dawned. Now it is as though it should have been cut down, but the merciful one intercedes with the merciful one. He wanted to show how merciful he was, and so he stood up to himself with a plea for mercy" (Augustine, Sermons).
Writing about the identify of the vineyard worker, St. Cyril of Alexandra says, "If any one should say that the vinedresser is the Son, this view also has a suitable reason on its side. He is our Advocate with the Father, our propitiation, and the gardener of our souls. He constantly prunes away whatever is harmful and fills us with rational and holy seeds so we may produce fruits for him" (Cyril of Alexandria, Commentary on Luke).
Whether we identify the fig tree as Israel, humanity, or both, the point is the same: God, in his great mercy, is patient, longsuffering, and does not will to bring judgment and condemnation on any. The message of his grace comes over and over to his creation through the proclamation of the Word so that we will stop resisting the work of the Spirit to draw us near in faith. At the very least, we shall be without excuse.