2 For it is God, my beloved, even the God Who at first established the feast for us, Who vouchsafes the celebration of it year by year. He both brought about the slaying of His Son for salvation, and gave us this reason for the holy feast, to which every year bears witness, as often as at this season the feast is proclaimed. This also leads us on from the cross through this world to that which is before us, and God produces even now from it the joy of glorious salvation, bringing us to the same assembly, and in every place uniting all of us in spirit; appointing us common prayers, and a common grace proceeding from the feast. For this is the marvel of His loving-kindness, that He should gather together in the same place those who are at a distance; and make those who appear to be far off in the body, to be near together in unity of spirit.
Source: Letters (New Advent)