From Dom Guéranger's The Liturgical Year.

The Church announces to us, to-day, in her Office of Lauds, these solemn words:

Nolite timere: quinta enim die veniet ad vos Dominus noster.
Fear not: for on the fifth day, our Lord will come unto you.

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. Let us pray to him with confidence. In that heaven of light and vision, where his repentance and love have placed him, he will intercede for us, and gain for us that docility of mind and heart, which will enable us to see and recognize Him, who is the Expected of nations, and who, though the King of the world, will give no other signs of His majesty, than the swaddling-clothes and tears of a Babe. But let us first read the acts of our holy apostle. The Church has deemed it prudent to give us them in an exceedingly abridged form, which contains only the most reliable facts, gathered from authentic sources; and thus she excludes all those details, which have no historic authority.

Thomas apostolus, qui et Didymus, Galilaeus, post acceptum Spiritum sanctum, in multas provincias profectus est ad prædicandum Christi Evangelium. Parthis, Medis, Persis, Hircanis, et Bactris christianæ fidei et vitæ praecepta tradidit. Postremo ad Indos se conferens, eos in Christiana religione erudivit. Qui ad extremum, vitæ doctrinæque sanctitate, et miraculorum magnitudine, quum cæteris omnibus sui admirationem, et Jesu Christi amorem commovisset, illius gentis regem, idolorum cultorem, magis ad iram accendit: cujus sententia condemnatus, telisque confossus, Calaminæ apostolatus honorem martyrii corona decoravit.
Thomas the apostle, who was also named Didymus, was a Galilean. After he had received the Holy Ghost, he travelled through many provinces, preaching the Gospel of Christ. He taught the principles of Christian faith and practice to the Parthians, Medes, Persians, Hircanians, and Bactrians. He finally went to the Indies, and instructed the inhabitants of those countries in the Christian religion. Up to the last, he gained for himself the esteem of all men by the holiness of his life and teaching, and by the wonderful miracles he wrought. He stirred up, also, in their hearts, the love of Jesus Christ. The king of those parts, a worshipper of idols, was, on the contrary, only the more irritated by all these things. He condemned the saint to be pierced to death by javelins: which punishment was inflicted at Calamina, and gave Thomas the highest honour of his apostolate, the crown of martyrdom.

 

The Great Antiphon of St. Thomas

 

O Thoma Didyme! qui Christum meruisti cernere; te precibus rogamus altisonis, succurre nobis miseris; ne 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.

Prayer

Da nobis, quæsumus, Domine, beati apostoli tui Thomæ solemnitatibus gloriari: ut ejus semper et patrociniis sublevemur, et fidem congrua devotione sectemur. Per Dominum, &c. Amen.
Grant, O Lord, we beseech thee, that we may rejoice on the solemnity of thy blessed apostle, Thomas; to the end that we may always have the assistance of his prayers, and zealously profess the faith he taught. Through Jesus Christ our Lord. Amen.

The following prayer is from the Matins of the Gothic, or Mozarabic, breviary:

Domine Jesu Christe, qui posuisti in capite martyris tui Thomæ apostoli coronam de lapide pretioso, in fundamento fundatam; ut non confundatur,quia in te credidit; coronetur, quia pro te animam posuit: sit ergo intercessionibus ejus in nobis famulis tuis fides vera, qua te etiam coram persecutoribus promptissima devotione confiteamur: quatenus interveniente tanto martyre, coram te et angelis tuis minime confundamur. Amen.
O Lord Jesus Christ, who hast placed on the head of thy martyr, Thomas the apostle, a crown made of that precious stone, that is founded in the foundation; that so he might not be confounded, because he believed in thee; nor be uncrowned, because he laid down his life for thee; may there be, by his intercession, in us thy servants, that true faith, whereby we may confess thee with most ready hearts before persecutors: that thus, by the same great martyr’s intercession, we may not be confounded before thee and thy angels. Amen.

The Greek Church celebrates, with her usual solemnity, the feast of St. Thomas; but she keeps it on the sixth of October. We extract the following stanzas from her hymns.

Hymn of St. Thomas
(Taken from the Menæa of the Greeks)

Domini palpato latere, bonorum assecutus es summitatem; nam velut spongia hinc hausisti latices, fontem bonorum, æternamque potasti vitam, mentibus expellens ignorantiam, divinaque Dei cognitionis dogmata scaturire faciens.

Tua incredulitate et tua fide stabilisti tentatos, nunciare incipiens omni creaturae Deum ac Dominum, carne pro nobis in terris indutum, crucem mortemque subeuntem, clavis perforatum, cujus lancea latus apertum, ex quo vitam haurimus.

Indorum omnem terram fulgere fecisti, sacratissime, ac Deum videns apostole! Quum enim illuminasses filios luminis et diei, horum, in Spiritu, sapiens, idolica evertisti templa, et sublimasti eos in charitate Dei ad laudem et gloriam Ecclesiæ, beate intercessor pro animabus nostris.

Divina videns, Christi Sapientiæ spiritualis demonstratus es crater mysticus, O Thoma apostole, in quem fidelium animæ laetantur, et Spiritus sagena populos eruisti ex abysso ignorantiæ: unde ex Sion sicut fluvius devenisti charitatis, tua divina scaturire faciens dogmata in omnem creaturam. Christi Passionis imitatus, latere pro ipso perforatus, induisti immortalitatem: illum deprecare misereri animabus nostris.
When thy hand touched Jesus’ side, thou didst find the perfection of good things; for, as a mystic sponge, thou didst thence imbibe the water of life, the fount of all that is good, and didst drink in everlasting life; whereby thou didst cleanse men’s minds from ignorance, giving them to drink of the divine dogmas of the knowledge of God.

Thou didst, by thine own incredulity and thy after-faith, confirm such as were tempted; for thou didst proclaim to all men, how he, that is thy Lord and thy God, became incarnate on this earth for us, was nailed to the cross and suffered death, and had his side opened with a spear, whence we draw life.

Thou didst make all the Indies shine with much light, O most holy apostle, thou contemplator of the Divinity! For after thou hadst enlightened these people, and made them to be children of the light and day, thou, by the Spirit of God, didst wisely overthrow the temples of their idols, and didst elevate the people to the love of God, making them an honour and a glory to the Church, O thou that helpest us by thy intercession!

By the vision thou hadst of divine things, thou becamest, O apostle Thomas! the mystic cup of the Wisdom of Christ, which gives joy to the souls of the faithful. Thou wert the spiritual net, drawing men from the sea of ignorance. Hence is it, that thou camest from Sion as a stream of charity, watering the world with the divine dogmas. Thou didst imitate the Passion of Jesus, thou wert pierced in thy side, thou hast put on immortality. Pray to God, that he have mercy on our souls.

O glorious apostle, Thomas! who didst lead to Christ so many unbelieving nations, hear now the prayers of the faithful, who beseech thee to lead them to that same Jesus, who, in five days, will have shown Himself to His Church. That we may merit to appear in His divine presence, we need, before all other graces, the light which leads to Him. That light is faith; then, pray that we may have faith. Heretofore, our Saviour had compassion on thy weakness, and deigned to remove from thee the doubt of Hishaving risen from the grave; pray to Him for us, that He will mercifully come to our assistance, and make Himself felt by our heart. We ask not, O holy apostle! to see Him with the eyes of our body, but with those of our faith; for He said to thee, when He showed Himself to thee: ‘Blessed are they who have not seen, and have believed!’ Of this happy number we desire to be. We beseech thee, therefore, pray that we may obtain the faith of the heart and will, that so, when we behold the divine Infant wrapped in swaddling-clothes and laid in a manger, we may cry out: ‘My Lord! and my God!’ Pray, O holy apostle, for the nations thou didst evangelize, but which have fallen back again into the shades of death. May the day soon come, when the Sun of justice will once more shine upon them. Bless the efforts of those apostolic men, who have devoted their labours and their very lives to the work of the missions; pray that the days of darkness may be shortened, and that the countries, which were watered by thy blood, may at length see that kingdom of God established amongst them, which thou didst preach to them, and for which we also are in waiting.