Trinity Sunday is the feast of the Holy Trinity — the one God in three Persons, Father, Son, and Holy Spirit. It falls on the first Sunday after Pentecost, completing the great arc of the liturgical calendar: the Father sends the Son (Christmas), the Son accomplishes redemption (Easter), the Spirit is given to the Church (Pentecost), and on Trinity Sunday the Church confesses the fullness of God as revealed through these mighty acts. Unlike most feasts, Trinity Sunday commemorates not an event but a doctrine — the central mystery of the Christian faith. The feast is comparatively late in origin. While Trinitarian theology was definitively settled at Nicaea (325) and Constantinople (381), a distinct feast of the Trinity did not become widespread until the medieval period. Individual bishops promoted it — Thomas Becket, consecrated on Trinity Sunday 1162, established it at Canterbury. Pope John XXII made it universal for the Western church in 1334. The BCP tradition, however, gave Trinity Sunday a structural importance beyond Rome's: in the English Prayer Book tradition, the Sundays of the long season after Pentecost are numbered 'after Trinity' rather than 'after Pentecost,' making Trinity Sunday the hinge of the entire second half of the church year. The BCP 2019 lists it among the seven Principal Feasts, and the Athanasian Creed — the most detailed creedal exposition of Trinitarian doctrine — is traditionally appointed for this day.

Trinity Sunday's liturgical tradition reflects the challenge of celebrating a doctrine rather than a narrative. The appointed readings across the three-year lectionary cycle present different facets of Trinitarian revelation: Nicodemus's nighttime conversation with Jesus (John 3), the baptismal commission 'in the name of the Father and of the Son and of the Holy Spirit' (Matthew 28), and Paul's Trinitarian benediction (2 Corinthians 13:14). The Athanasian Creed (Quicunque Vult), with its precise and paradoxical formulations — 'neither confounding the Persons nor dividing the Substance' — has been associated with this feast since at least the ninth century in the West, and the BCP 2019 includes it among its historical documents. The collect for Trinity Sunday is among the most theologically careful in the Prayer Book: '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.' Cranmer's 1549 language echoes here. The white or gold vestments used on this day reflect its status as a feast of the Godhead. In Anglican practice, numbering Sundays 'after Trinity' rather than 'after Pentecost' has given this feast a unique structural role — it names half the church year.

Luke 1:39-56 records the visitation. After the Annunciation, Mary 'rose up in those days' and went 'into the hill country' to visit Elizabeth, the mother of John the Baptist. Luke notes that Elizabeth was 'in her sixth month' (of pregnancy), while Mary had just conceived Jesus—placing the visitation chronologically six months before John's nativity.

When Mary greeted Elizabeth, the unborn John 'leaped in the womb,' and Elizabeth was 'filled with the Holy Spirit.' She cried out in a loud voice: 'Blessed are you among women, and blessed is the fruit of your womb! And why has this happened to me, that the mother of my Lord comes to me?' Elizabeth's recognition of Mary as 'the mother of my Lord' is theologically significant: the unborn John bore witness to the unborn Jesus; the Holy Spirit filled Elizabeth with prophetic knowledge.

In response to Elizabeth's greeting, Mary sang her great canticle, the Magnificat (Luke 1:46-55): 'My soul magnifies the Lord, and my spirit rejoices in God my Savior, for he has looked with favor on the lowliness of his servant.... He has brought down the powerful from their thrones and lifted up the lowly; he has filled the hungry with good things and sent the rich away empty.'

The Magnificat is a revolutionary hymn of divine justice and mercy, echoing the song of Hannah (1 Samuel 2:1-10) and the themes of the Psalms. It celebrates God's preferential option for the lowly and his overturning of human hierarchies. Mary remained with Elizabeth 'about three months' (through the birth of John) and then returned to her home.

The May 31 date (or June 1 in some traditions) has been observed since at least the late medieval period, though the feast was not universally standardized until later. The feast celebrates not merely a historical event but a moment of encounter between the two greatest figures of the Old Testament order (John, the last of the prophets) and the New Testament order (Jesus, the Son of God). It marks the moment when the 'great things' God promised to do for Mary began to unfold in history.

Traditionally, the Visitation is understood as a moment of profound encounter between the old and new covenants—between John, the greatest of the prophets, and Jesus, the Messiah. The greeting of Elizabeth and the leap of John in the womb are seen as a form of witness and honor to the incarnate Son of God. The Magnificat has been sung daily in the Christian Church at Evening Prayer (Vespers) since ancient times and is one of the most beloved prayers in Christian tradition. Mary's voluntary journey to serve and care for her elderly cousin is portrayed as an example of Christian charity and humility.