From Dom Guéranger's The Liturgical Year.

Prope est jam Dominus; venite, adoremus.

De Isaia Propheta.

Cap. xxx.

Exspectat Dominus ut misereatur vestri, et idea exaltabitur parcens vobis; quia Deus judicii Dominus, beati omnes qui exspectant eum. Populus enim Sion habitabit in Jerusalem: plorans nequaquam plorabis: miserans miserebitur tui: ad vocem clamoris tui statina ut audierit, respondebit tibi. Et dabit vobis Dominus panem arctum, et aquam brevem: et non faciet avolare a te ultra doctorem tuum, et erunt oculi tui videntes præceptorem tuum. Et dabitur pluvia semini tuo, ubicumque seminaveris in terra: et panis frugum terrae erit uberrimus et pinguis. Pascetur in possessione tua in die illo agnus spatiose, et tauri tui, et pulli asinorum, qui operantur terram, commixtum migma comedent sicut in area ventilatum est. Et erunt super omnem montem excelsum, et super omnem collem elevatum rivi currentium aquarum in die interfectionis multorum, cum ceciderint turres. Et erit lux lunæ sicut lux solis, et lux solis erit septempliciter sicut lux septem dierum, in die qua alligaverit Dominus vulnus populi sui, et percussuram plagæ ejus sanaverit. Ecce nomen Domini venit de longinquo, ardens furor ejus, et gravis ad portandum: labia ejus repleta sunt indignatione, et lingua ejus quasi ignis devorans. Spiritus ejus velut torrens inundans usque ad medium colli, ad perdendas Gentes in nihilum, et frenum erroris quod erat in maxillis populorum.
The Lord is now nigh; come, let us adore.

From the Prophet Isaias.

Ch. xxx.

The Lord waiteth that he may have mercy on you, and therefore shall he be exalted sparing you: because the Lord is the God of judgement, blessed are all they that wait for him. For the people of Sion shall dwell in Jerusalem: weeping thou shalt not weep: he will surely have pity on thee: at the voice of thy cry, as soon as he shall hear, he will answer thee. And the Lord will give you spare bread and short water: and will not cause thy teacher to flee away from thee any more, and thy eyes shall see thy teacher. And rain shall be given to thy seed, wheresoever thou shalt sow in the land: and the bread of the corn of the land shall be most plentiful and fat. The lamb in that day shall feed at large in thy possession, and thy oxen, and the ass-colts, that till the ground, shall eat mingled provender as it was winnowed in the floor. And there shall be upon every high mountain, and upon every elevated hill, rivers of running waters in the day of the slaughter of many, when the towers shall fall. And the light of the moon shall be as the light of the sun, and the light of the sun shall be sevenfold as the light of seven days, in the day when the Lord shall bind up the wound of his people, and shall heal the stroke of their wound. Behold the name of the Lord cometh from afar, his wrath burneth, and is heavy to bear: his lips are filled with indignation, and his tongue as a devouring fire. His breath as a torrent overflowing even to the midst of the neck, to destroy the nations unto nothing, and the bridle of error that was in the jaws of the people.

And are we then to weep no more, O Jesus? Happy we! How could we be sad now that Thou hast heard our prayers, and our eyes shall behold Thee, our Master, and our Teacher? If Thou yet delayest some days longer, it is only that we may have more time to receive what Thou hast made it Thy glory to give—mercy and the pardon of our sins. Oh, the happiness of Thy kingdom! Oh, the richness of our lands, that is, of our souls, when Thy dew shall have fallen upon them! Oh, the sweetness of our Bread, which is to be Thyself, O living Bread come down from heaven! Oh, the brightness of the light which Thou wilt give us, even on the very day when Thou wilt have bound up our wounds! Blessed day, come quickly! And thou, dear night, when Mary is to give her divine Babe to us, when wilt thou come? So great is our hope in this Thy merciful coming, that we listen with less dread to the awful words of Thy prophet, who, with a rapidity swift as Thine own word, passes over the long ages between the two events, and speaks to us of the approach of the terrible day, when Thou wilt come suddenly in Thy burning wrath, with Thy lips filed with indignation, and Thy tongue as a devouring fire. Our present feeling is hope, for we are looking forward to that coming, in which Thou art the beautiful Prince of peace and love, and we cannot but hope. When that last day comes, have mercy on us! but on this day of Thine amiable visit, permit us to say to Thee the words of one of Thy servants: ‘Yes, dear Jesus, come; come to us! but in swathing-bands, not with Thy hand raised to punish us: in humility, not in Thy greatness: in the crib, not in the clouds of heaven: in the arms of Thy Mother, not on the throne of Thy Majesty: on the colt of the ass, not on the Cherubim: to us, and not against us: to save us, and not to judge: to visit us in Thy peace, not to condemn us in Thy anger. If Thou comest unto us thus, O Jesus! it is not from Thee, but to Thee, that we will flee.’ (The venerable Peter of Celles, First sermon of Advent.)

Hymn Taken from the Anthology of the Greeks
(December 20)

Bethlehem, præparare, omnibus aperitur Eden; lætare, Ephrata, quia arbor vitae in spelunca effloruit ex Virgine; ejus enim venter paradisus demonstratus est spiritualis, in quo est divina planta, de qua manducantes vivimus; neque enim amplius sicut Adam moriemur: nam Christus nascitur, lapsam principio relevans imaginem.

Ministraturus Christus libenter progreditur, plasmatis formam plastes accipit; qui locuples est divinitate, Adam indigenti novam reformationem atque nativitatem ut commiserans elargitur.

Inclinans cœlos et in Virgine habitans progreditur carnaliter, Bethlehem in spelunca pariendus, ut scriptum est, videndus que infantulus qui infantes in vulva vivificat; ipsi gaudentes nunc obviemus omnes corde veloci.

Dominus nascens ut hospes, sapienter in propria venit: recipiamus eum, ut hospites factos paradisi deliciarum iterum habitare faciat natus in spelunca.

Jam divinæ Verbi Incarnationis omnibus aperitur propylæum; cœli, gaudete; angeli, exsultate; lætetur terra cum hominibus, una cum pastoribus et magis in spiritu.

Fert sicut unguentum spirituale non vacuum Virgo alabastrum, et illud gestat in spelunca in spiritu ad evacuandum sapienter illud, ut bono odore repleat animas nostras.

Angelicæ accurrite Virtutes; qui in Bethlehem estis, præparate præsepium, Christus enim nascitur; Sapientia progreditur. Accipe salutationem, Ecclesia; in gaudium Dei Matris dicamus, populi: Benedictus qui venit, Deus noster.

Christus Deus noster manifeste gradiens veniet, et non tardabit; ex nuptinescia nympha videbitur; in spelunca autem requiescet; et tu, præsepe alogorum, quem cœlum non continet, accipe fasciis in te involvendum, qui uno verbo nostras alogias solvit.

Chorum age, Isaia, Verbum Dei demonstra, prophetiza puellæ Mariæ rubum incendiari et igne non consumi. Splendore Deitatis, Bethlehem, adomare; aperi januam, O Eden; atque iter capite magi, Salutem visuri in præsepio fasciatum; quem sidus designavit desuper speluncam, vitæ datorem Dominum salvantem genus nostrum.
Be thou ready, O Bethlehem, for now Eden is open unto all; rejoice, O Ephrata, for the tree of life has blossomed in the cave from the Virgin; for her womb has become a mystic paradise, wherein is the divine plant, of which if we eat we shall live, and not, like Adam, die; for Christ is born, that he may raise up his image which had fallen in the beginning.

Christ comes willingly to minister to us; the Creator puts on the creature’s form; he that is rich in the Godhead, mercifully bestows on the needy Adam a new creation and birth.

He has bowed down the heavens, and, taking up his abode in the Virgin, he comes in our flesh to be born in Bethlehem’s cave, as it is written; and he that gives life to children in the womb has himself become a child: let us all go forth to meet him with our hearts full of ardour and joy.

The all-wise Lord thus born, comes among his own to receive hospitality from his own creatures; let us receive him, that this divine Babe of the cave may make us the guests of the paradise of delights.

Now is the portal of the divine Incarnation opened to all: be glad, ye heavens i exult with joy, all ye angels! let the earth and its inhabitants rejoice in spirit with the shepherds and the magi.

The Virgin, as a precious vase of alabaster, bears the divine perfume into the cave, there wisely and ineffably to yield what she contains, that she may fill our souls with the delicious fragrance.

Ye angelic Powers: hasten thither. Ye who dwell in Bethlehem, prepare the crib, for Christ is coming to be born; Wisdom advances towards you. Receive our greetings, O thou Church of God! and let us, O ye people, thus sing in honour of the divine Mother’s joy: Blessed be our God, that cometh!

Christ our God shall come manifestly, and shall not delay; he shall appear born of a spotless Virgin; he shall be laid in a cave; and thou, the crib of senseless beasts, receive into thyself, wrapt in swathing-bands, him, whom the heavens cannot contain, and whose single word absolves our senseless sins.

Sing, O Isaias! show us the Word of God, predict the bush that is to be on fire, yet not consumed; the Virgin Mary. Put on thy splendour, the rays reflected from the Deity, O Bethlehem! open thy gates, O Eden! Set out on your journey, ye Magi, to see the Saviour laid in swaddling-clothes in a manger, Him whom your star, standing over the cave, pointed out to you the Lord and giver of life, the Saviour of our race.

Prayer from the Gallican Missal
(In Adventu Domini, Immolatio)

Vere dignum et justum est, nos tibi hic et ubique semper gratias agere, Domine sancte, Pater omnipotens, æterne Deus, cui proprium est veniam delictis impendere, quam pœnaliter imminere. Qui fabricam tui operis per eumdem rursus lapidem es dignatus erigere, ne imago, quae ad similitudinem tui facta fuerat vivens, dissimilis haberetur ex morte. Munus venialis indulgentiae praestitisti: ut unde mortem peccato contraxerat, inde vitam pietas repararet immensa. Haec postquam prophetica sæpius vox praedixit; et Gabriel angelus Mariæ jam praesentia nuntiavit, mox puellæcredentis in utero, fidelis Verbi mansit aspirata conceptio; et illa proles nascendi sub lege latuit, quae cuncta suo nasci nutu concessit. Tumebatur Virginis sinus; et fœcunditate suorum viscerum corpus mirabatur intactum. Grande mundo spondebatur auxilium, fœminæ partus sine viro mysterium; quando nullius maculae nebula fuscata tenso nutriebat ventre præcordia, mox futura sui genitrix genitoris.
Truly is it meet and just that here and in allplaces we should give thee thanks, O holy Lord, almighty Father, eternal God, who lovest rather to pardon than to punish sin. Who didst mercifully use in the restoration of thy work the same stone wherewith thou hadst made it, lest the image made to thy likeness living, should, dying, become unlike thee. Thou didst bestow on man the gift of an indulgent pardon; that thence thy boundless mercy might restore life, whence man by his sin had wrought death. It is this that the voice of the prophets had often foretold; it is this that the angel Gabriel announced to Mary as then to be presently accomplished. The Virgin believed, and, in that same hour, there was conceived in her womb the long-sighed-for Word, ever faithful to his promises. There did her Child lie concealed until the law, which fixed the time of birth, had been observed, though it was he, whose sovereign will granted all things to be born. The Virgin was seen to be a Mother; it was the prodigy of there being in the same body an immense fruitfulness and an angelic purity. Great was the help augured to the world by this mystery of a Virgin Mother, whereby the Mother of her own Creator nourished him in her womb, she whose purity was undimmed by the least shadow of a stain.