The night prayer of the third Sunday of Advent sees a new invitatory. The song that had awakened the clerics in the middle of the night on previous Sundays had been:
Regem venturum Dominum venite adoremus

Come, let us worship the Lord King who is about to come
This is a song with a very practical value: "et dicit per invitatorium ad Ecclesiam invitari" (and the invitatory is said to invite [the faithful] to church). Amalarius of Metz (9th century) describes the intonation of this antiphon as a "tuba cantoris signum" (a signal, almost an order or invitation given by the cantor's trumpet) whose purpose is "excitare christiani circumquaque" (calling Christians from all around) so that they may flock to prayer. Prayer is described as schola, an opportunity to listen and learn from the doctors and pastors of the Church who speak to us through the liturgy. From the third Sunday of Advent until Christmas Eve, the invitatory antiphon that opens the nocturnes is:
Prope est jam Dominus venite adoremus

The Lord is now near, come let us worship
It is a cry of gladness that breaks into this expectation of the Church as she sees the coming of her Lord ever closer. From this Sunday, the very adverb "prope" (near) begins to appear with greater frequency, almost yearning insistence, in the liturgical texts.
After the invitatory and almost obeying what was sung in the psalm that followed its antiphon: "praeoccupemus faciem ejus in confession et In psalmis jubilemus ei" (Let us draw near to him to give him thanks, to him let us acclaim with songs of joy. Ps 95:2), the 12 psalms were sung.
As for the other Sundays of this Advent season, the first responsory that is sung in the night seems to be clothed with a value, not only symbolic, but also as a hermeneutical key. At the reading of the beginning of chapter 26 of Isaiah "In die illa cantabitur canticum" (On that day this song shall be sung) followed this responsory:
Ecce apparebit Dominus super nubem candidam, et cum eo sanctorum milia; et habens in vestimento et in femore suo scriptum: rex regum, et Dominus dominantium.

Behold, the Lord will appear on a white cloud, and with him a thousand saints. And he shall have in his garments and on his thighbone written, King of kings and Lord of lords.

The text of this responsory seems to echo the vision described in Revelation, "I looked again, and behold, a white cloud, and on the cloud one sat, resembling a Son of Man" (Rev. 14:14) and again, " One name is written on his cloak and on his thighbone: King of kings and Lord of lords" (Rev. 19:16). The ear and liturgical understanding of those who, until a few decades ago, pondered these texts in song could not remain indifferent to one detail. Here is certainly an explicit quotation from the book of Revelation but, at the same time, it seems an implicit quotation from that responsory they had sung 15 days earlier, "Aspiciens a longe ecce video dei potentiam venientem et nebulam totam terram tegentem." The power of God that is coming to meet humanity begins, now, to take a name: He is the King of kings and Lord of lords.
The third Sunday of Advent is certainly known to be the Sunday . Gaudete. The theme of joy gently enters its liturgy. The night's readings seem not to hint at it and, the texts of the Church Fathers, even present a reflection on fasting: "Fiat refectio pauperis, abstinentia ieiunanti"! (Let the poor be fed, let those who are experiencing the fast of this time abstain). so admonished in the second nocturnal the sermon of Pope Leo. The Advent season, unlike today, was a time of fasting and penance. As Lent presents a Sunday of refectio (refreshment), the fourth called Laetare, on that model Advent also experiences it on the third. The meaning of this celebration, then, can be grasped in fullness only by thinking of the seriousness of an Advent journey that was not only sentimental but included a penitential dimension that resulted precisely in fasting. (To this day the tradition is preserved in many monastic communities, even beginning from after the feast of St. Martin.)
Because the need to meditate, in the Sunday Gaudete, on a reading that talked about fasting?

The third Sunday of Advent began the week that saw the fasting of the Four Tempora, which was practiced on the following Wednesday, Friday and Saturday. Although Advent was also a time of austerity, these fasts belonged to a general institution of the liturgical year.
The prophet Zechariah's warning was heard, "Thus says the Lord of hosts: The fasting of the fourth, fifth, seventh and tenth month shall be changed for the house of Judah into joy and rejoicing and days of feasting, provided you love truth and peace" (Zech 8:19). December, in this reckoning, corresponds to the tenth month. In the fast of the feria sexta (Sabbath), moreover, presbyteral ordinations were taking place. Why?
In the 12th century the explanation was this: "quia illa dies Spiritui Sancto est consecrata" (because that day is consecrated to the Holy Spirit) and was in response to the divine precept contained in the book of Exodus: "Remember the Sabbath day to keep it holy" (Ex. 20:8) and, consequently, "quia recipiunt dona Spiritus Sancti in ordinibus, tali die ordinantur" (since [Presbyters] receive the gifts of the Holy Spirit at ordination, on that day they are consecrated). This applied only to presbyters since episcopal ordinations were to be celebrated on Sunday "ad ostendendum, quod ipse est vicarius apostolorum, qui in die dominica, scilicet in die Pentecostes, virtutem Spiritus Sancti ex alto susceperunt" (to show that they are vicars of the Apostles who on the Sunday day, that is, Pentecost, received, from above, the gift of the Holy Spirit).

Turning now to the Mass we can make a few remarks about the famous introit Gaudete.
Gaudete in Domino semper iterum dico gaudete modestia vestra nota sit omnibus hominibus dominus prope est nihil solliciti sitis sed in omni oratione petitiones vestrae innotescant apud Deum.

Rejoice always in the Lord: I repeat: rejoice. Let your modesty be manifest to all men: the Lord is near. Do not be anxious about anything, but in all circumstances make your needs known to God (Phil. 4:4-5)
Certainly there are many commentaries on this passage that insist on the theme of joy. It is surprising, then, that a theologian like William of Auxerre places, instead, the hint on the meaning of expectation of the Second Advent present in this text. The exegesis he proposes of the passage from Ephesians sounds like this: "Apostolus enim non loquitur de primo adventu, cum dicit: "Dominus prope est ", sed de secundo, unde invitat ad gaudium spirituale, per quod firmiter expectamus gaudia secundi adventus" (The Apostle, in fact, is not speaking to us of the first Advent when he says 'The Lord is at hand,' but of the second for which he invites spiritual rejoicing so that, with firmness, we await the joys of the second Advent.) Spiritual joy is described as the necessary condition, which is why it is repeated twice, "dulciter sustinere omnia aspera mundi, ut nichil avellat nos a spe aeternorum" (to endure gently all the harshness of the world, so that nothing can snatch us from the hope of eternity). How to preserve this joy in the pilgrimage toward the coming of the Lord? "Huius gaudii custos est modestia" (With the modesty that is the guardian of this joy). Modesty is not only a virtue but is a fruit of the Spirit as we can read in the letter to the Galatians, "Instead, the fruit of the Spirit is love, joy, peace, patience, longsuffering, kindness, gentleness, meekness, faithfulness, modesty, continence, chastity" (Gal 5:22-23). In the Epistle, which presented Paul's text to the Philippians in its entirety (Phil 4:4-7), there was further elaboration of the theme of this joy: "hoc gaudium, quod est pax menti" (this joy is peace of mind). Indeed, we read: "Et pax Dei, quae exsuperat omnem sensum, custodiat corda vestra, et intelligentias vestras, in Christo Iesu Domino nostro" (And the peace of God, which surpasses all understanding, will guard your hearts and minds in Christ Jesus our Lord).
The Responsorial Gradual, like the Hallelujah, sees the text from Psalm 80: "You, shepherd of Israel, listen, you who lead Joseph like a flock. Sitting on the cherubim you shine before Ephraim, Benjamin and Manasseh. Awaken your power and come to our rescue."
Qui sedes Domine super Cherubim excita potentiam tuam et veni [ut salvos faciat nos]


Rising on the cherubim you shine, awaken your power and come [to our rescue] (Ps. 80 2-3).
A portion of text is missing from Psalm 80: "before Ephraim, Benjamin and Manasseh," which was equally interpreted from its etymological and moral meaning whereby: Ephraim: "id est fructificantem in bonis operibus" (i.e., bearing fruit in good works); Benjamin: "id est filium dextre" (i.e., son of the right [i.e., "of fortune"]) and Manasseh "qui oblitus est terrenorum" (who forgets earthly things). These three realities tell us about the Judgment and consequently project us into the Second Advent.
In addition to Psalm 80, it is Psalm 85 that returns twice in this liturgy. It, in fact, forms the introit verse and the text of the offertory and is read as a witness to the first Advent of the Lord:
Benedixisti domine terram tuam avertisti captivitatem Jacob remisisti iniquitatem plebis tuae

Thou hast blessed, O Lord, thy land: thou delivered Jacob from bondage: thou forgave the iniquity of thy people. (Ps. 85:2).
The communion antiphon presents a text from the prophet Isaiah:
Dicite pusillanimes confortamini et nolite timere ecce Deus noster veniet et salvabit nos

Say to the lost in heart, Courage! Fear not; behold your God comes and will save us
The musical writing seems to insist precisely on the need to comfort the pusillanimous. This word is to be understood in the sense of a person lacking in willpower and fortitude. This emphasis on the rhetoric of the Gregorian melody is also confirmed by the medieval theological interpretation that tells us, "Oportet enim, quod pusillanimes confortentur ad hoc, ut sustineant tribulationes, et sic expectent cum fiducia secundum adventum" (For it is necessary for the pusillanimous to be comforted for this reason: so that they may endure tribulation and thus await the Second Advent with confidence.)