This Sunday is the Feast of the Purification of Our Lady. The Gospel is St Luke 2:22-32:
22 Et postquam impleti sunt dies purgationis ejus secundum legem Moysi, tulerunt illum in Jerusalem, ut sisterent eum Domino, 23 sicut scriptum est in lege Domini: Quia omne masculinum adaperiens vulvam, sanctum Domino vocabitur: 24 et ut darent hostiam secundum quod dictum est in lege Domini, par turturum, aut duos pullos columbarum. 25 Et ecce homo erat in Jerusalem, cui nomen Simeon, et homo iste justus, et timoratus, exspectans consolationem Israël: et Spiritus Sanctus erat in eo. 26 Et responsum acceperat a Spiritu Sancto, non visurum se mortem, nisi prius videret Christum Domini. 27 Et venit in spiritu in templum. Et cum inducerent puerum Jesum parentes ejus, ut facerent secundum consuetudinem legis pro eo, 28 et ipse accepit eum in ulnas suas: et benedixit Deum, et dixit: 29 Nunc dimittis servum tuum Domine, secundum verbum tuum in pace: 30 quia viderunt oculi mei salutare tuum, 31 quod parasti ante faciem omnium populorum: 32 lumen ad revelationem gentium, et gloriam plebis tuæ Israël.
And in the Douay-Rheims version:
 And after the days of her purification, according to the law of Moses, were accomplished, they carried him to Jerusalem, to present him to the Lord:  As it is written in the law of the Lord: Every male opening the womb shall be called holy to the Lord:  And to offer a sacrifice, according as it is written in the law of the Lord, a pair of turtledoves, or two young pigeons:  And behold there was a man in Jerusalem named Simeon, and this man was just and devout, waiting for the consolation of Israel; and the Holy Ghost was in him. And he had received an answer from the Holy Ghost, that he should not see death, before he had seen the Christ of the Lord.  And he came by the Spirit into the temple. And when his parents brought in the child Jesus, to do for him according to the custom of the law,  He also took him into his arms, and blessed God, and said:
 Now thou dost dismiss thy servant, O Lord, according to thy word in peace;  Because my eyes have seen thy salvation, Which thou hast prepared before the face of all peoples:  A light to the revelation of the Gentiles, and the glory of thy people Israel.
Here are the Third Nocturn readings for Matins by St Ambrose (from Divinum Officium, but arranged as for the Benedictine Office):
(Reading 9): And, behold, there was a man in Jerusalem, whose name was Simeon, and the same man was just and devout, waiting for the consolation of Israel. The birth of the Lord is attested not only by Angels and Prophets, and shepherds, but also by elders and just men. Every age, and both sexes, as well as the miracles of the events themselves, are here to strengthen our faith.
(Reading 10): A virgin conceiveth, a barren woman beareth, a dumb man speaketh, Elizabeth prophesieth, the wise man worshippeth, the unborn child leapeth, the widow praiseth, and the just man waiteth.Well is he called just, who looked not for favour for himself, but for consolation for his people. He desired to be set free from the bondage of this frail body, but he waited to see the Promised One for he knew that blessed are the eyes that see Him.
(Reading 11): Then took he Him up in his arms, and blessed God, and said Lord, now lettest Thou thy servant depart in peace, according to thy word. Behold a just man, confined in the weary prison of the body, desiring to be dissolved and to begin to be with Christ. For to be dissolved and to be with Christ is much better. Whosoever will be dissolved and be with Christ, let him come into the Temple, let him come to Jerusalem, let him wait for the Lord's Christ, let him take hold on the Word of God, let him embrace it with good works, as it were with arms of faith and then let him depart in peace, for he shall not see death, who hath seen life.
(Reading 12): Behold how the Lord's Birth doth overflow with abounding grace for all, and prophecy is not denied to the just, but to the unbelieving. Behold, Simeon prophesieth that the Lord Jesus Christ is come for the fall and rising again of many yea, He shall separate the just from the unjust by their deserts, and according as our work shall be, so shall the true and righteous Judge command us to be punished or rewarded.
Canticle of Simeon
The Nunc Dimittis (verses 29-32 of the Gospel) is only used in the Benedictine Office on those few occasions where the Roman Rite has come to displace St Benedict's prescriptions, such as during the Easter Triduum. In the Roman office though, it is traditionally sung daily at Compline. Here is a beautiful modern setting by Geoffrey Burgon.