Introitus Ad te levávi ánimam meam: Deus meus, in te confído, non erubescam: neque irrídeant me inimíci mei: étenim universi, qui te exspectant, non confundentur. V. Vias tuas, Dómine, demonstra mihi: et sémitas tuas édoce me. Gloria Patri. Sicut erat. Ad te levávi.
Introit To Thee have I lifted up my soul: in Thee, o my God, do I trust, let me not be put to shame; nor let my enemies mock me, for all they that await Thee shall not be confounded. V. Show me Thy ways, o Lord and teach me Thy paths. Glory be to the Father... As it was in the beginning... To Thee have I lifted up my soul...
At the Mass (of the First Sunday of Advent), the Introit is Ad te levavi, because through the coming of the Lord into the flesh, hope is most greatly lifted up, “For God so loved the world that He gave His only Son” (John 3, 16), and again “He did not spare His own Son” (Romans 8, 32), etc. And note that if some are roused, others nevertheless languish in sleep; therefore the cantor, beginning with “To Thee have I lifted up my soul”, by raising up his voice goes from the lower (note) to the higher, which is typical of one rousing others up. And this is noted also in the Epistle (Rom. 13, 11-14), where it says, “Now is the hour to rise from sleep.” There follows the verse, “Show me Thy ways, o Lord,” because Christ when He comes shows us His ways, whence Isaiah says (2, 2 and 3), “The mountain of the house of the Lord shall be (prepared) etc. Come, and let us go up to the mountain of the Lord, and to the house of the God of Jacob, and He will teach us His ways.” And the Epistle... shows what those ways are: “Knowing that the hour is nigh for us to rise from sleep.” For in the part where it says, “The night hath passed, and the day approacheth,” the effect (of the Incarnation) is indicated, since day came about when the Sun was born; and therefore it follows, “As in the day, let us walk honestly”, that is, in all good works, “and put ye on the Lord, Jesus Christ”, that we may thus be sons of God, because it was for the sake of this that the Son of God became man, that man might become a son of God. (William Durandus, Rationale Divinorum Officiorum, 6.3.15)
