Super flumina Babylonis illic sedimus et flevimus: dum recordaremur tui, Sion. (Offertory for the Twentieth Sunday after Pentecost, cf. Psalm cxxxvi, 1: "Upon the rivers of Babylon there we sat and wept; when we remembered thee, O Sion.")
“The waters of Babylon” are all things which here are loved, and pass away. One man, for example, loves to practice husbandry, to grow rich thereby, to employ his mind therein, thence to gain pleasure: let him observe the issue, and see that what he has loved is not a foundation of Jerusalem, but a stream of Babylon. Another says, 'It is a grand thing to be a soldier: all husbandmen fear those who are soldiers.'
But then other citizens of the holy Jerusalem, understanding their captivity, mark how the natural wishes and the various lusts of men hurry and drag them hither and thither, and drive them into the sea; they see this, and they throw not themselves into the waters of Babylon, but “sit down and weep,” either for those who are being carried away by them, or themselves whose deserts have placed them in Babylon, but sitting, that is, humbling themselves.
O holy Sion, where all stands firm and nothing flows! Who has thrown us headlong into this? Why have we left your Founder and your society? Behold, placed where all things are flowing and gliding away, scarce one, if he can grasp the tree, shall be snatched from the stream and escape.
Humbling ourselves then in our captivity, let us “sit by the waters of Babylon,” let us not dare to plunge ourselves in those streams, nor to be proud and lifted up in the evil and sadness of our captivity, but let us sit, and so weep. Let us sit “by” the waters, not beneath the waters, of Babylon; such be our humility, that it will not overwhelm us. Sit “by” the waters, not “in” the waters, not “under” the waters; but yet sit, in humble fashion, talk not as one would in Jerusalem.
For many weep with the weeping of Babylon, because they rejoice also with the joy of Babylon. When men rejoice at gains and weep at losses, both are of Babylon. One ought to weep, but in the remembrance of Sion. If one weeps in the remembrance of Sion, one ought to weep even when it is well with oneself in Babylon. ...
Brethren, let not your instruments of music rest in your work: sing one to another songs of Sion. Readily have you heard; the more readily do what you have heard, if you wish not to be willows of Babylon fed by its streams, and bringing no fruit. But sigh for the everlasting Jerusalem: whither your hope goes before, let your life follow; there we shall be with Christ. [Sed suspirate in aeternam Ierusalem; quo praecedit spes vestra, sequatur vita vestra: ibi erimus cum Christo.]
Christ now is our Head; now He rules us from above; in that city He will fold us to Himself; we shall be equal to the Angels of God. We should not dare to imagine this of ourselves - did not the Truth promise it? This then desire, brethren, this day and night think on. ...
Let the Rock conquer. Be built upon the Rock, if ye desire not to be swept away either by the stream, or the winds, or the rain. If ye wish to be armed against temptations in this world, let longing for the everlasting Jerusalem grow and be strengthened in your hearts. Your captivity will pass away, your happiness will come; the last enemy shall be destroyed, and we shall triumph with our King, without death.
Enarratio in Psalmum CXXXVI
Enarratio in Psalmum CXXXVI