This is a sermon that Augustine gave at one Easter Vigil, explaining what we do in our liturgical celebrations of what happened once and for all:We know and believe most firmly, brothers and sisters, that Christ died once for us, the righteous one for sinners, the Lord for servants, the free one for captives, the physician for the ill, the blessed one for the wretched, the rich one for the poor, the seeker for the lost, the redeemer for the sold, the shepherd for the flock, andwhat is more wondrous than all elsethe Creator for the creature. He remained, of course, what he had always been and handed over what he had become; hidden God, manifest man, by his power giving life, in his weakness dying, unchangeable in his divinity, suffering in his fleshthe One of whom the Apostle says: He was handed over because of our sins, and rose for the sake of our justification (Rom 4:25).You know very well that this was done once and for all. And, yet this feast repeats, as if it happens more often in the course of time, what the Scriptures in many places proclaim was done once. But we shouldnt think the truth and the feast to be contrary to one another, the one deceiving, the other telling the truth. For what the truth points to as having happened once in reality, the feast renews by celebrating it often in pious hearts. Truth reveals what happened as it happened; the feast, not by repeating it but by celebrating it, does not permit even the past to be past [nec praeterita praeterire permittit]. Finally, Christ our Passover [Pascha] has been sacrificed (1 Cor 5:7). He was killed once, and dies now no more; death has no more dominion over him (Rom 6:9). Thus according to the voice of truth, we say that his Passover occurred once and will not occur again; but in terms of this feast, we say every year that his Passover [Easter] will come.This is how I believe what was said in the Psalm should be interpreted: The thought of man will confess to you, and the remains of thought will celebrate a solemn day to you (Ps 75:11). For unless human thought committed to memory what was really done in the course of time, it would not be able to find any remains of it later. The thought of a person gazing on the truth confesses to the Lord, and the remains of his thought, which are in the memory, at stated times do not cease to celebrate feasts so that the thought will not be considered ungrateful. That is what this nights splendid feast is for, when by our vigil and through the remains of our thought we enact the resurrection of the Lord which in our thought we confess to have happened once.... This feast has made this night shine throughout the world. (Augustine, Sermon 220)