Trinity Sunday occurs one week after Pentecost and celebrates “the one and equal glory” of Father, Son, and Holy Spirit. Like Pentecost, it is one of the seven principal feasts of the church year (Book of Common Prayer, p 15). Trinity Sunday originated on the church’s calendar in 1334. This feast is associated with Thomas Becket who was consecrated bishop on Trinity Sunday, 1162. This martyr’s popularity may be the source of the past custom of naming the remaining Sundays of the church year “Sundays after Trinity.” The 1928 Book of Common Prayer followed this practice. The 1979 Book of Common Prayer names these Sundays “Sundays after Pentecost”. The propers for Trinity Sunday are only used on Trinity Sunday and not (as usual after a major feast) during the subsequent week. In some traditions, the Thursday after Trinity Sunday is the Feast of Corpus Christi commemorating the institution of the Eucharist by Jesus on Maundy Thursday. Because Holy Week emphasizes Jesus’ Passion, another day of the calendar was chosen for a celebration of our Lord’s Eucharist. Hymn 320 was written by Thomas Aquinas for this feast’s gospel hymn and hymns 329-331 were written by him for its vespers (albeit references to transubstantiation have been omitted).
~Dr. Gil Haas