From Dom Guéranger's The Liturgical Year.
Regem venturum Dominum, venite, adoremus.
De Isaia Propheta.
Emitte Agnum Domine, dominatorem terræ, de petra deserti ad montem filiæ Sion. Et erit: sicut avis fugiens, et pulli de nido avolantes, sic erunt filiae Moab in transcensu Arnon. Ini consilium, coge concilium, pone quasi noctem umbram tuam in meridie: absconde fugientes, et vagos ne prodas. Habitabunt apud te profugi mei: Moab, esto latibulum eorum a facie vastatoris. Finitus est enim pulvis, consummatus est miser, defecit qui conculcabat terram. Et praeparabitur in misericordia solium, et sedebit super illud in veritate, in tabernaculo David, judicans et quaerens judicium, et velociter reddens quod justum est.
Come, let us adore the King our Lord, who is to come.
From the Prophet Isaias.
Send forth, O Lord, the Lamb, the ruler of the earth, from Petra of the desert to the mount of the daughter of Sion. And it shall come to pass, that as a bird fleeing away, and as young ones flying out of the nest, so shall the daughters of Moab be in the passage of Arnon. Take counsel, gather a council, make thy shadow as the night in the midday: hide them that flee, and betray not them that wander about. My fugitives shall dwell with thee: O Moab, be thou a covert to them from the face of the destroyer. For the dust is at an end, the wretch is consumed, he hath failed that trod the earth under foot. And a throne shall be prepared in mercy, and one shall sit upon it in truth in the tabernacle of David, judging and seeking judgement, and quickly rendering that which is just.
Send forth to us, O Lord, the Lamb: 'It is the Lamb,’ says Peter of Celles,' it is the Lamb we need, and not the Lion; the Lamb that knows no anger, and whose meekness is never ruffled; the Lamb that will give us His snow-white wool to warm our coldness, and cover our nakedness; the Lamb that will give us His flesh to eat, lest we faint with hunger on the way. Send Him full of wisdom, for in His divine prudence He will vanquish the spirit of pride; send full of strength, for it is written that the Lord is strong and mighty in battle; send Him full of meekness, for He is to come down as dew that falls on the fleece; send Him as a victim, for He is to be sold and immolated for our ransom; send Him the pardoner of sinners, for He is to come to call them, and not the just; send Him to receive power and divinity, for He is worthy to loose the seven seals of the sealed book, the unspeakable mystery of the Incarnation.’ Thou art King, then, O divine Lamb! Thou art even now, in thy Mother’s womb, the sovereign Ruler. This virginal womb is a throne of mercy whereon Thou art seated in humility, ready to avenge our rights and confound our cruel enemy. O most dear King! our eyes cannot yet behold Thee, but our hearts tell us Thou art near us. We know that it is for our sake that Thou hast put on this strange royalty. Suffer us to approach Thee, and offer Thee our homage and loyalty, even now that a cloud hides Thee from our sight. . A few days more, and Thou wilt be seated on another throne, Thy Mother’s arms, and then all the earth will see the salvation that is sent unto it.
Hymn taken from the Anthology of the Greeks
Spelunca, parare; Agna enim venit fœtum gerens Christum: recipe, præsepium, illum qui nos terrigenas verbo solvit ineffabili modo: pastores de nocte vigilantes, prodigiosum confitemini miraculum; magique e Perside aurum, thus et myrrham Regi afferte: quia visus est e Virgine matre Dominus, quem et ipsa prona servili modo, mater adoravit et ei quem in brachiis suis tenebat dixit: Quomodo in me inseminatus es: vel quomodo in me ingeneratus es, Salvator meus et Deus?
Audi cœlum, et intellige terra; ecce enim Filius Verbumque Dei Patris progreditur ad nascendum ex Virgine, inexperta virum, sine dolore illum pariente et virtute Spiritus sancti. Bethlehem parare: aperi januam, Eden, nam qui Est fit qui non erat, et plasturgus omnis creaturæ plasmatur ipse, afferens mundo magnam misericordiam.
Natura immense, Christe Rex, quomodo parva te recipiet spelunca? Quomodo præsepe te poterit continere, Jesu, ex Matre nesciente virum, advena factus in propria, ut hospites ipse salves?
Novum facta cœlum, Domina, e vulva tua, sicut e nebula Christum solem gloriae oriri facere festines in spelunca carnaliter, omnes terrae fines suis splendoribus fulgentissime irradiaturum, per incommensurabilem misericordiam.
Noscis nostrum dolorem et miseriam, misericors Christe, et nos non despicis; sed exinanis temctipsum, non adhuc egressus ex tua genitrice; tabernaculumque figens in matrice nuptinescia, quæ sine dolore te pariet in spelunca caro factum.
Montes et colles, valles et campi, populi et tribus, gentes ac omnis spiritus, alalagmum agite; lætitiæ divinæ venit plenitudo, omnium advenit redemptio, Verbum Dei tempora nesciens per misericordiam factum sub tempore.
Vitis divina incorruptam maturitate nigrescere faciens uvam, appropinquat: paritura venit lætitiæ vinum scaturiens et nos bibere faciens ipsi canentes: Deus noster, benedictus es!
Myrotheca divina, intus myrum ferens graditur, ut in spelunca Bethlehem effundat illud a quo mystico replentur odore canentes: Deus patrum, benedictus es!
Forceps quam olim vidit Isaias propheta, divinum carbonem Christum in utero geris omnem materiam peccati comburentem, fideliumque animas illuminantem.
Finem habuerunt prophetarum præconia; quem enim praenuntiarunt in temporis plenitudine venturum, adest, apparet casta ex Virgine corporatus; illum puris mentibus excipiamus.
Cave of Bethlehem, be ready, for here comes the Mother bearing Christ, her Lamb, in her womb; and thou, O crib, receive him who delivers us mortals by his word ineffably; ye shepherds, keeping your nightwatch, tell the wondrous miracle; ye Magi, from Persia, bring to the King gold, incense, and myrrh; for the Lord hath appeared, born of a Virgin Mother; before him she herself falls down, and though his Mother, yet adores him as his lowly handmaid, and then taking him into her arms, she says unto him: O my Saviour, my God, how is it that thou camest unto me, and wast produced in me?
Hear, O ye heavens, and thou, O earth, attend: the Son and Word of God the Father is to be born of a Virgin that knows not man, and travails not when giving him birth, for all is by the power of the Holy Ghost. Bethlehem, be ready! Eden, open thy gates! for he that Is is made what he was not, and he that formed all creatures receives himself a created form, bringing to the world plentiful mercy.
O thou that art immense by Nature, O Christ our Ring, how shall a little cave receive thee? How shall a crib contain thee, O Jesus, Son of a spotless Virgin, making thyself a stranger in thine own house, that thou mayst give salvation to them that harbour thee?
Thou art a new heaven, O Lady! Hasten to make arise from thy womb, as from a cloud, Christ, the Sun of glory; may he appear in the flesh, in the cave, shedding thence to the ends of the world his dazzling splendour by his immense mercy.
Thou knowest, O merciful Jesus, our pains and misery, and thou despisest us not; but emptiest thyself even before leaving thy Mother’s virginal womb, where thou hast set thy tabernacle; this thy Mother will not travail in giving thee birth in the cave, thee who art made flesh.
Mountains and hills, valleys and plains, peoples and tribes, nations and every spirit, sing the song of victory! the fullness of a divine joy is coming, and all are to be redeemed, for the Word of God, who is beyond all time, is now made in time.
Now is coming towards us the heavenly vine, on which has ripened the immortal fruit; she comes to produco for us the wine of Joy, of which she will give us to drink: we will then sing to him, Blessed art thou our God!
There is advancing the vessel bearing the divine perfume, and she will place it in the cave of Bethlehem, and we, filled with the mystic fragrance, will sing, Blessed art thou, O God of our fathers!
Thou, O Mary, art like that instrument which Isaias saw of old, holding in thy womb the Christ, who, like a burning coal, will consume all the dross of sin, and will enlighten the minds of the faithful.
The songs of the prophets are hushed; for he, whom they announced as having to come in the fullness of time, is present and appears to us, having assumed a body from the chaste Virgin; let us receive him with pure hearts.
Prayer from the Mozarabic Missal
(Second Sunday of Advent)
Jucundatur, Domine, et tripudiat terra; quia Verbum caro factum habitat in sacrae Virginis membra. In cujus adventu omnis de captivitate redimitur terra; quae detinebatur per transgressionem Adæ in obscurata gehenna. Nunc moveatur mare, et omnia quae in eo sunt; montes exsultent et omnia ligna silvarum; quia Deus homo dignatur, per uterum beatae Virginis Mariae, de cœlo in mundum venire. Per ipsius igitur adventum te deprecamur, omnipotens Deus, ut nostræ camis fragilitatem a vinoulis peccatorum absolvas, et praesenti familiae tuæ misericordia plenus occurras.
The earth is glad, O Lord, and leaps with joy, for that the Word made flesh dwells in the womb of the holy Virgin. At his coming, the whole earth is ransomed from captivity, after having been kept, by Adam’s sin, in a dark prison. Now let the sea be moved, and all things that are therein; let the mountains leap with joy, and all the trees of the forests; because God, having become man, has deigned to come, through the womb of the blessed Virgin Mary, from heaven into this world. By this his coming, therefore, we beseech thee, O almighty God, that thou loose the weakness of our flesh from the bonds of sin, and come, in thy overflowing mercy, to the assistance of this thy family here present before thee.
 Third Sermon for Advent.