Easter Triduum, Holy Triduum, or Paschal Triduum is the period of three days that begins with the Mass of the Lord's Supper on the evening of Maundy Thursday and ends with The Great Vigil of Easter. It recalls the passion, death, burial, and resurrection of Jesus, as portrayed in the canonical Gospels. Even though the period of time covered is 3 days the Church historically views the events as one service.
The Great Vigil of Easter finds us gathering the following day in that empty place. We find ourselves remind of the desolation and emptiness of the night before. It is held in the hours of darkness between sunset on Holy Saturday and sunrise on Easter Day — most commonly in the evening of Holy Saturday — and is the first celebration of Easter, days traditionally being considered to begin at sunset.
The Easter Vigil is the most important service of public worship and Mass of the liturgical year; in the that it is the first celebration of the Gloria during the fifty-day long celebration of Easter, marked by the first use since the beginning of Lent of the exclamatory "Alleluia", a distinctive feature of the Easter season. The service parts which are celebrated during the Easter Vigil are unique to that night and are the most elaborate and important of the ecclesiastical year and usher in the fifty-day long celebration which ends on the Day of Pentecost.
The service normally consists of four parts:
- The Service of Light.
- The Service of Lessons.
- Christian Initiation, or the Renewal of Baptismal Vows.
- The Holy Eucharist with the administration of Easter Communion.
The Service of Light begins outside with the “New Fire”...The Pascal Candle is lit and leads the procession into the Sanctuary. It is announced “The Light of Christ” to which we respond “Thanks be to God”. We are reminded that Christ is the “light” in the darkness of life for Christians everywhere. The Exsultet (also called the "Easter Proclamation" or "Paschal Praeconium") is sung, after which the people take their seats as the liturgy of the word begins.
The Liturgy of the Word consists of readings from the Old Testament. The account of the Israelites' crossing of the Red Sea is given particular attention in the readings since this event is at the center of the Jewish Passover, which Christians believe Christ's death and resurrection is the fulfillment of. Each reading is followed by a psalm or biblical canticle (i.e., Psalm 10, Exodus 15:1-18, Psalm 30, Isaiah 12:2-6, Psalm 19, Psalm 42 & 43) recited responsorially and a prayer relating what has been read in the Old Testament to the Mystery of Christ. After these readings conclude, the candles are lit on the altar and the Gloria in Excelsis Deo is sung for the first time since before Lent. The opening collect is read. The reading from the Epistle to the Romans (i.e., Romans 6:3-11) is proclaimed, followed by Psalm 118. The Gospel of the Resurrection (i.e., Matthew 28:1-10; Mark 16:1-8 or Luke 24:1-12) then follows, along with the first sermon of Easter.
After the conclusion of the Liturgy of the Word, the water of the baptismal font is solemnly blessed and the congregation renews their baptismal vows and receive the sprinkling of baptismal water. The prayers of the faithful follow.
After the prayers, the Liturgy of the Eucharist continues as usual. This service concluded with the solemn blessing of Easter and brings to end the Triduum.
Here is a quote from the Easter Sermon of St. John Chrysostom which I think is a fitting reminder of what this day is for all who claim the Victory in Jesus Christ:
“Wherefore, enter ye all into the joy of your Lord;
Receive your reward,
Both the first, and likewise the second.
You rich and poor together, hold high festival!
You sober and you heedless, honour the day!
Rejoice today, both you who have fasted
And you who have disregarded the fast.
The table is full-laden; feast ye all sumptuously.
The calf is fatted; let no one go hungry away.
Enjoy ye all the feast of faith:
Receive ye all the riches of loving-kindness.
Let no one bewail his poverty,
For the universal Kingdom has been revealed.
Let no one weep for his iniquities,
For pardon has shown forth from the grave.
Let no one fear death,
For the Saviour's death has set us free.
He that was held prisoner of it has annihilated it.”