6 One then who has been admonished, and it may be moved to compunction by these words, may ask what is good? What is the nature of good? And whence it comes? Well is it that you have understood that it is your duty to ask this. I will answer your enquiries, and will say, “That is good which you can not lose against your will.” For gold you may lose even against your will; and so you can a house; and honours, and even the health of the body; but the good whereby you are truly good, you neither receive against your will, nor lose it against your will.
I enquire then, “What is the nature of this good?” One of the Psalms teaches us an important matter, perchance it is even this that we are seeking for. For it says, “O you sons of men, how long will you be heavy in heart?” How long will that tree be in its three years fruitlessness? “O you sons of men, how long will you be heavy in heart?” What is “heavy in heart”? “Why do ye love vanity, and seek after leasing?” And then it goes on to say what we must really seek after; “Know ye that the Lord has magnified His Holy One?” Now Christ has come, now has He been magnified, now has He risen again, and ascended into heaven, now is His Name preached through the world: “How long will you be heavy in heart?”
Let the times past suffice; now that that Holy One has been magnified, “How long will you be heavy in heart?” After the three years, what remains but the ax? “How long will you be heavy in heart? Why do ye love vanity, and seek after leasing?” Vain, useless, frivolous, fleeting things are these still sought after, now that Christ the Holy One has been so magnified? Truth now is crying aloud, and is vanity still sought after? “How long will you be heavy in heart?”
Source: Sermons on Selected Lessons of the New Testament (New Advent)