While he was yet an Anglican, John Henry Newman became familiar with the Roman Breviary; indeed, I know of evidence that that in the 1840s Tractarian young men may have been far more familiar with the Breviary than with the Missal. And Newman was particularly haunted by the great "O" antiphons which we sing at Vespers during these last great ferias of Advent. Among these antiphons, Newman could not forget the antiphon O Adonai of December 18.
In his semi-autobiographical novel Loss and Gain (which I would urge all admirers of Newman to reread in these months before his beatification), he first quotes the Great antiphons when he is writing of the Holy Sacrifice of the Mass: "And as Moses on the mountain, so we too make haste and bow our heads to the earth and adore. So we, all around, each in his place, look out for the great Advent, waiting for the moving of the water. ... It is wonderful! Quite wonderful! When will thesedear good people be enlightened? O Sapientia, fortiter suaviterque disponens omnia, O Adonai, O Clavis David et expectaio gentium, veni ad salvandum nos, Domine Deus noster."
And in the climax of the book, when Charles Reding is present for the first time at Benediction, "the truth flashed upon him, fearfully yet sweetly; it was the Blessed Sacrament - it was the Lord Incarnate who was on the Altar, who had come to visit and to bless His people. It was the great Presence, which makes a Catholic Church different from every other place in the world; which makes it holy as no other place can be holy. The Breviary offices were by this time not unknown to Reding: and as he threw himself on the pavement, in sudden self-abasement and joy, some words of those great Antiphons came into his mouth, from which Willis had formerly quoted: O Adonai, et Dux domus Israel, qui Moysi in rubo apparuisti; O Emmanuel, Expectatio Gentium et Salvator earum, veni ad salvandum nos, Domine Deus noster".
YHWH, the God of Israel and of our forefathers, in His Advent and in His Incarnation - He, the great End and fulfilment of all things - is present as bow before the Host. Therefore we before Him bending, this great Sacrament revere; types and shadows have their ending, for the newer rite is here.