Trinity Sunday

Trinity Sunday, observed on the Sunday after Pentecost, is the only feast in the Western liturgical calendar that commemorates a doctrine rather than an event in the economy of salvation. The day calls the Church to contemplate the mystery at the heart of the Christian God: one divine Being eternally existing as three co-equal persons — Father, Son, and Holy Spirit.

The BCP 2019 Collect for Trinity Sunday is the ancient Trinitarian doxology cast in the second-person address of collect form. The Athanasian Creed (Quicunque Vult), listed among the historic formularies of Anglicanism, is appointed for use at Morning Prayer on this day in some traditions.

The weeks that follow Trinity Sunday are reckoned in the BCP calendar as Sundays after Pentecost, numbered ordinally. Trinity Sunday thus serves as the threshold between the christological half of the church year (Advent through Pentecost) and the season of growth in the life of the Spirit.

For most of the first Christian millennium, the Sunday after Pentecost carried no feast of its own, and Rome resisted giving it one. When a petition for a special day reached Pope Alexander II in the 1060s, he refused it, on the ground that the Roman Church already honored the Trinity every day: in the Gloria Patri appended to the psalms, and in the ordinary shape of the Eucharist itself. A separate feast, on this reasoning, was not merely unnecessary but slightly beside the point, since the same logic that called for a day dedicated to the Trinity would just as easily call for one dedicated to the Divine Unity, and neither truth is more or less true on any other Sunday of the year. The Micrologus, an eleventh-century treatise on Roman liturgical customs usually associated with Bernold of Constance, records this same Roman reluctance and treats an already-circulating votive office for the Trinity, kept in some places on the Octave of Pentecost, as unauthorized.

Local churches, meanwhile, went their own way. Stephen, bishop of Liège in the early tenth century, is credited with composing an early Office of the Holy Trinity, which some dioceses took up for the Sunday after Pentecost and others reserved instead for the Sunday before Advent. By the early twelfth century the custom had spread widely enough that the Benedictine abbot Rupert of Deutz wrote in its defense. England's own attachment to the day owes something to Thomas Becket, who was consecrated Archbishop of Canterbury on the Sunday after Pentecost, 3 June 1162. English tradition credits him with securing, or at least popularizing, the keeping of that Sunday as Trinity Sunday, a custom said to have spread outward from Canterbury. The connection is old and often repeated, but it rests on later English testimony rather than a contemporary decree in Becket's own hand, so it is best treated as a long-standing tradition rather than a settled fact.

The feast became universal only in 1334, in the last year of the Avignon pontificate of Pope John XXII, who extended it to the whole Western Church and fixed it on the first Sunday after Pentecost. The office he adopted for the occasion had been written a generation or two earlier by the Franciscan friar John Peckham, who would himself later become Archbishop of Canterbury before his death in 1292. Two future archbishops of Canterbury, then, stand at either end of the feast's slow passage from local custom to universal observance.

The day's own collect shows what that long argument was finally settled in favor of. It asks not for the memory of an event but for grace to make a confession: "by the confession of a true faith, to acknowledge the glory of the eternal Trinity, and in the power of your divine Majesty to worship the Unity." Every other Sunday from Advent to Pentecost had told a story: the Son's coming, his life, death, and rising, the Spirit's descent on the Church. Trinity Sunday turns from narrating what God has done to confessing who God is, before the long season that follows opens.

There is no single narrative behind Trinity Sunday the way the Transfiguration or the Annunciation each has one. Instead the day gathers texts the Church has long read as glimpses of the Trinity's own life. The clearest is the baptismal formula in Matthew 28:16-20, where the risen Christ commands his disciples to baptize "in the name of the Father and of the Son and of the Holy Spirit," one name shared by three. Paul's closing benediction in 2 Corinthians 13:14 names all three Persons by what each gives the Church: "the grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit."

Isaiah 6:1-8, the prophet's vision of the Lord high and lifted up, surrounded by seraphim crying "Holy, holy, holy," stands behind the Sanctus sung at every celebration of the Eucharist, even though the vision itself long predates any explicit doctrine of the Trinity. And the farewell discourse of John 14-16 is the New Testament's fullest sustained Trinitarian scene: the Son speaking of the Father who sent him and of the Spirit, the Advocate, whom the Father will send in the Son's name.

Trinity Sunday's own liturgy has always been spare next to the great festivals around it. There is no narrative to preach and no procession to stage. The classical Prayer Book tradition marked the day chiefly by appointing the Athanasian Creed, the Quicunque Vult, to be said or sung at Morning Prayer in place of the Apostles' Creed, letting the creed's own long and careful language of Trinity carry the day rather than adding a sermon's worth of application to it.

What the day asks of a worshipper is not to remember an event but to hold still before a confession: not what God has done this year, but who God has always been, before creation, before Bethlehem, before Pentecost. The love that moves within the Trinity itself, the Father's love for the Son, returned, and poured out as the Spirit, is not a puzzle solved once a year and set aside. It is the love the Church has already been baptized into.

White is the color of the day, as for every feast of the Lord, and its vestments and hangings often carry over into the first Sunday or two of the season that follows, before green returns for the long run of ordinary Sundays through summer and autumn.

The Athanasian Creed's link to the day is old and, in the classical Prayer Book tradition, textually specific: the 1662 Book of Common Prayer appointed the Quicunque Vult for Morning Prayer on Trinity Sunday and a handful of other major feasts, in place of the Apostles' Creed. Its use has declined sharply since, in part because of its length and its anathemas against those who deny its teaching, and most contemporary Anglican prayer books no longer require it. ACNA's 2019 Book of Common Prayer permits the Athanasian Creed as an option among the additional directions for the Eucharist and prints its full text among the Prayer Book's documentary foundations, but the day's ordinary liturgy no longer depends on it.

The season that follows has long been called Trinitytide in the English tradition, its Sundays numbered "after Trinity" rather than "after Pentecost." The two namings track the same weeks and reflect different emphases rather than a disagreement about the calendar.

The day has also given the Church one of its best-loved hymns. Reginald Heber, later bishop of Calcutta, wrote "Holy, Holy, Holy! Lord God Almighty" explicitly for Trinity Sunday, drawing its opening acclamation from the same vision in Isaiah together with the worship of the four living creatures and twenty-four elders in Revelation 4. Published only after Heber's death in 1826, it was set to John Bacchus Dykes's tune Nicaea in the influential 1861 hymnal Hymns Ancient and Modern, a tune-name that quietly nods to the council that first defended the doctrine the hymn sings.