Upon the rivers of Babylon, there we sat and wept, when we remembered thee, o Zion. (The Offertory chant of the 20th Sunday after Pentecost.)
The bodily captivity (of which the Offertory speaks) signifies our spiritual captivity; the return from captivity is the forgiveness of sins. ... Therefore, lest we return to a similar captivity, and be shut out of the wedding feast (in last week’s Gospel, Matthew 22, 1-14), Paul warns us in the Epistle, “See to it that ye walk with care, not as the unwise, but as the wise.” The Introit Omnia quae fecisti is the voice of Daniel remembering that past captivity, and ascribing it to the judgment of God; likewise, in the Offertory, we weep over that captivity, but in the Gradual Oculi omnium, we give thanks (for deliverance from it). - William Durandus, Rationale Divinorum Officiorum 6.137 in fine.This text has also been used by some of finest composers of liturgical polyphony, including Palestrina,
Orlando de Lassus (an historical recording from 1961),
and Victoria, who was having a particularly good day when he wrote this.
