20 Moreover, as to this fruit of the olive, if the matter be examined, you will find what it was. The fruit of the olive signifies charity. How do we prove this? Just as oil is kept down by no liquid, but bursting through all, bounds up and overtops them; so likewise charity cannot be pressed to the bottom, but must of necessity show itself at the top. Therefore the apostle says of it, “Yet show I unto you a more excellent way.” Since we have said of oil that it overtops other liquids, in case it should not be of charity, the apostle said, “I show you a more excellent way,” let us hear what follows. “Though I speak with the tongues of men and of angels, and have not charity, I have become as sounding brass, or a tinkling cymbal.” Go now, Donatus, and cry, “I am eloquent;” go now, and cry, “I am learned.” How far eloquent? How far learned? Have you spoken with the tongues of angels? Yet though you were to speak with the tongues of angels, not having charity, I should hear only sounding brass and tinkling cymbals. I want solidity; let me find fruit among the leaves; let there be not words merely, let them have the olive, let them return to the ark.
Source: Tractates on the Gospel of John (New Advent)