"For the Mass of the Lord's Supper there is the gift of Christ in the Eucharist, this gift which is an image of his own gift upon the Cross. The liturgy itself, it concludes with this kind of Eucharistic procession and then we wait with Christ in the midst of his Passion."
The foot washing, O'Malley said, "is actually very interesting, it was often done in monasteries, where the guests would have their feet washed. It entered into the liturgy itself, where there would be the washing of the feet of the 12, as the sort of image of washing of the 12 apostles."
Latin for 'darkness,' Tenebrae is a form of the Liturgy of the Hours on the eve of Holy Thursday, which prepares the participants for the coming darkness of Christ's death and his descent into hell.
With roots in the ninth century, Tenebrae vigils were once celebrated at most parishes throughout Holy Week, and included Psalms and Lamentation readings and the extinction of candles.
"It involved the reading of Lamentations, the gradual extinction of candles, and then the sort of beating of the pews that you would hear to represent the noise of Christ descending into darkness to transform it," said O'Malley.
Tenebrae liturgies are still celebrated in many parishes.
Good Friday of the Lord's Passion:
The Good Friday liturgy is not a Mass, but a service reflecting on the Passion of Christ and the power of the cross.
Participants listen to the scripture of Christ's passion and venerate the cross. Worshipers kiss the cross, a practice recorded by the fourth-century pilgrim Egeria. While the cross is kissed, O'Malley said, two ancient hymns are sung: the Reproaches and the Pange Lingua.
The Reproaches, or the Improperia, are a series of chants and responses, which reflect on Christ's lamentations during his Passion. One of the lines is "I led you out of Egypt, from slavery to freedom, but you led your Savior to the cross."
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Written by the St. Fortunatus, the Pange Lingua celebrates the life-giving power of Christ's Passion. O'Malley said the hymn "describes the cross as this flowering of new life, the tree of life rather than the tree of death."
Good Friday's liturgy does not include the Eucharistic consecration, O'Malley said, but the Holy Eucharist is already sanctified and distributed to the worshipers.
At the Easter Vigil, the Paschal candle is blessed and lit outside the Church, and worshippers assemble with unlit candles. As the priests process to the altar, the fire of Christ's light is passed from candle to candle within the Church.
The Easter Vigil is the pinnacle of the Triduum, said O'Malley, drawing attention to Christ's light, which abolishes darkness, and to his salvation, which is now opened to the catechumens.
"All candles have been extinguished, all darkness has descended, now new light is lit in this Easter fire."