From Dom Guéranger's The Liturgical Year.

O Oriens, splendor lucis æternæ, et sol justitiæ; veni et illumina sedentesin tenebris, et umbra mortis.
O Orient! splendour of eternal light, and Sun of justice! come and enlighten them that sit in darkness, and in the shadow of death.

O Jesus, divine Sun! Thou art coming to snatch us from eternal night: blessed for ever be Thy infinite goodness! But Thou puttest our faith to the test, before showing Thyself in all Thy brightness. Thou hidest Thy rays, until the time decreed by Thy heavenly Father comes, in which all Thy beauty will break upon the world. Thou art traversing Judea; Thou art near Jerusalem; the journey of Mary and Joseph is nigh its term. Crowds of men pass or meet Thee on the road, each one hurrying to his native town, there to be enrolled, as the edict commands. Not one of all these suspects that Thou, O divine Orient! art so near him. They see Thy Mother Mary, and they see nothing in her above the rest of women; or if they are impressed by the majesty and incomparable modesty of this august Queen, it is but a vague feeling of surprise at there being such dignity in one so poor as she is; and they soon forget her again. If the Mother is thus an object of indifference to them, it is not to be expected that they will give even so much as a thought to her Child, that is net yet born. And yet this Child is Thyself, O Sun of justice! Oh! increase our faith, but increase, too, our love. If these men loved Thee, O Redeemer of mankind, Thou wouldst give them the grace to feel Thy presence. Their eyes, indeed, would not yet see Thee, but their hearts, at least, would burn within them, they would long for Thy coming, and would hasten it by their prayers and sighs. Dearest Jesus! who thus traversest the world Thou hast created, and who forcest not the homage of Thy creatures, we wish to keep near Thee during the rest of this Thy journey: we kiss the footsteps of her that carries Thee in her womb; we will not leave Thee, until we arrive together with Thee at Bethlehem, that house of bread, where, at last, our eyes will see Thee, O splendour of eternal light, our Lord and our God!

Prayer for the Time of Advent
(The Mozarabic breviary, Monday of the fifth week. Oratio)

Immane satis facinus video coram tuis, Deus Pater, oculis a reprobis perpetratum: qui, dum Filium tuum, prædicatum in Lege, contemnunt, in incredulitatis suæ voragine remanserunt; dum hi quibus non erat de eo nuntiatum, viderunt eum, et qui non audierunt, intelligentia contemplati sunt. Amove ergo, quæsumus, quidquid resistit tibi in opere, ut credulo pectore sic in nobis virgulta donorum praepolleant, ut radix humilitatis nunquam arescat. Amen.
O God, our Father! what horrid crime is this I see committed in thy presence by the reprobate Jews! They spurn thy Son, that was foretold in the Law, and remain in the gulf of their incredulity; whereas, they to whom he was not announced, have seen him; and they who heard not, contemplated him in their spirit. Remove, therefore, we beseech thee, from us all that resists thee in our conduct, that so, with a believing heart, we may in such manner bring forth the branches of thy gifts bestowed on us, as that the root of humility may never dry up within us. Amen.