1 Touching “the fig-tree” which had its three years' trial, and bare no fruit, and “the woman which was in an infirmity eighteen years,” hearken to what the Lord may grant me to say. The fig-tree is the human race. And the three years are the three times; one before the Law, the second under the Law, the third under grace. Now there is nothing unsuitable in understanding by “the fig-tree” the human race. For when the first man sinned, he covered his nakedness with fig-leaves; covered those members, from which we derive our birth.
For what before his sin should have been his glory, after sin became his shame. So before that, “they were naked, and were not ashamed.” For they had no reason to blush, when no sin had gone before; nor could they blush for their Creator's works, because they had not yet mingled any evil work of their own with the good works of their Creator. For they had not yet eaten of the tree of knowledge of good and evil, of which they had been forbidden to eat. After then that they had eaten and sinned, the human race sprang from them; that is, man from man, debtor from debtor, mortal from mortal, sinner from sinner.
In this “tree” then he entitles those, who through the whole range of time would not bear fruit; and for this cause the axe was hanging over the unfruitful tree. The gardener intercedes for it, punishment is deferred, that help may be administered. Now the gardener who intercedes, is every saint who within the Church prays for those who are without the Church. And what does he pray? “Lord, let it alone this year also;” that is, in this time of grace, spare the sinners, spare the unbelievers, spare the barren, spare the unfruitful.
“I will dig about it, and put a basket of dung about it; if it bear fruit, well; but if not, you shall come and cut it down.” “You shall come:” When? You shall come in judgment, when You shall come to judge the quick and dead. Meanwhile they are spared. But what is the “digging”? What is the “digging about it,” but the teaching lowliness and repentance? For a ditch is low ground. The basket of dung understand in its good effects. It is filthy, but it produces fruit. The gardener's filth is the sinner's sorrows. They who repent, repent in filthy robes; if, that is, they understand aright, and repent in truth. To this tree then is it said, “Repent ye, for the kingdom of heaven is at hand.”
Source: Sermons on Selected Lessons of the New Testament (New Advent)