1 We rejoice at your numbers, for you have come together with readiness and in greater numbers than we could have hoped. This it is that delights and consoles us in all the labors and dangers of this life, your love towards God, and pious zeal, and assured hope, and fervor of spirit. You heard when the psalm was read, “that the needy and poor man cries to God in this world.” For it is the voice, as you have often heard, and ought to remember, not of one man, and yet of one man; not of one, because the faithful are many— many grains groaning amid the chaff diffused throughout the whole world— but of one, because all are members of Christ, and thus one body.
This people, then, poor and needy, does not know to rejoice with the world: its grief is within, and its joy is within, where no one sees but He who listens to him who groans, and crowns him who hopes. The rejoicing of the world is vanity. With great expectation is it hoped for and it cannot, when it comes, be held fast. For this day which is a day of rejoicing in this city to the lost, tomorrow will, of course, cease to be; nor will they themselves be the same tomorrow that they are today.
And all things pass away, fly away, and vanish like smoke; and woe to those who love such things! For every soul follows what it loves. “All flesh is grass, and all the goodliness thereof as the flower of the field: the grass withers, the flower fades; but the word of the Lord abides forever.” Behold what you must love if you desire to abide for ever. But you had this to reply: How can I apprehend the word of God? “The Word was made flesh, and dwelt among us.”
Source: Tractates on the Gospel of John (New Advent)