Today is the feast of St. Thomas the Apostle, the feast has a rank of Double of the Second Class and is transferred this year to today as the Fourth Sunday of Advent was the 21st, the normal day of St. Thomas' celebration.
According to tradition St. Thomas preached the Gospel in Asia and the Indian sub-continent. He is believed to have founded, inter alia, the St. Thomas Christians on the West coast of India, one of several groups using the East-Syrian family of liturgies (see image at the bottom of this post).
The Benedictine liturgist Dom Prosper Guéranger has eloquent words for St. Thomas' feast:
"This is the last feast the Church keeps before the great one of the Nativity of her Lord and Spouse. She interrupts the greater ferias in order to pay her tribute of honour to Thomas, the apostle of Christ, whose glorious martyrdom has consecrated this twenty-first day of December, and has procured for the Christian people a powerful patron, who will introduce them to the divine Babe of Bethlehem. To none of the apostles could this day have been so fittingly assigned as to St. Thomas. It was St. Thomas whom we needed; St. Thomas, whose festal patronage would aid us to believe and hope in that God whom we see not, and who comes to us in silence and humility in order to try our faith. St. Thomas was once guilty of doubting, when he ought to have believed, and learnt the necessity of faith only by the sad experience of incredulity: he comes then most appropriately to defend us, by the power of his example and prayers, against the temptations which proud human reason might excite within us."
The liturgy of the day is festal and began with first Vespers of the feast yesterday on the fourth Sunday of Advent. Four pluvialistae in pariti assist the Hebdomadarius at Vespers and Lauds. At Mattins there are the usual nine lessons. At Lauds the antiphon on the Benedictus is proper Quia vidisti me, Thoma, credidisti: beati, qui non viderunt, et crediderunt, alleluia referring to the incident recorded in the Gospel of St. John about St. Thomas' doubt in the Risen LORD. A commemoration is then made of the Advent feria.
Festal hymn tones and psalmody are used at the Horae Minorae. At Mass, which is sung after Terce the Gloria and Creed are both sung and there is a commemoration of the Advent feria, the preface is that of the Apostle. At second Vespers there is a commemoration of the Advent feria with the 'O' antiphon O Rex gentium. Compline ends the celebration of St. Thomas' transferred feast. Dom Guéranger gives a medieval 'O antiphon' for St. Thomas found in several rites including that of Sarum:
O Thoma Didyme! qui Christum meruisti cernere; te precibus rogamus altisonis, succurre nobis miseris; no damnemur cum impiis, in adventu Judicis.
O Thomas Didymus! who didst merit to see Christ; we beseech thee, by most earnest supplication, help us miserable sinners, lest we be condemned with the ungodly, at the coming of the Judge.
According to the 'liturgical books of 1962' St. Thomas, considered so important by Dom Guéranger, is entirely omitted this year and the day is a feria. In the 1970-2002 calendar his feast has been permanently transferred to July 3rd, the date of the translation of his relics. Yet again, the inadequacy of the putative "Gregorian", "TLM", "ancient" 1962 rite is apparent.
Holy Apostle Thomas pray to God for us that we may be delivered from the affliction of the liturgical books of 1962.
Art: (Top) Wikipedia; a Russian Icon of St. Thomas, 18th century.
(Lower) Icon of St. Thomas in the Indian tradition.