From Dom Guéranger's The Liturgical Year.
Although the solemnity of September 29 celebrates the praises of all the nine glorious choirs, yet the piety of the faithful, in the latter ages, desired to have a special day consecrated to the Guardian Angels. Several churches having taken the initiative, and kept the feast under various rites and on different days, Paul V (1608) authorized its celebration ad libitum. Clement X (1670) established it by precept as a feast of double rite on October 2, the first free day after Michælmas, on which it thus remains in some way dependent.
It is of faith, on the testimony of the Scriptures and of unanimous tradition, that God commits to His angels the guardianship of men, who are called to contemplate
Him together with these blessed spirits in their common fatherland. Catholic theology teaches that this protection is extended to every member of the human race, without any distinction of just and sinners, infidels and baptized. To ward off dangers; to uphold man in his struggle against the demons; to awaken in him holy thoughts; to prevent him from sinning, and even, at times, to chastise him; to pray for him, and present his prayers to God: such is the office of the Guardian Angel. So special is his mission, that one angel does not undertake the guardianship of several persons simultaneously; so diligent is his care, that he follows his ward from the first day to the last of his mortal existence, receiving the soul as it quits this life, and bearing it from the feet of the sovereign Judge to the place it has merited in heaven, or to its temporary sojourn in the place of expiation and purification.
It is from the lowest of the nine choirs, the nearest to ourselves, that the Guardian Angels are for the most part selected. God reserves to the Seraphim, Cherubim, and Thrones the honour of forming His own immediate court. The Dominations, from the steps of His throne, preside over the government of the universe; the Virtues watch over the course of nature’s laws, the preservation of species, and the movements of the heavens; the Powers hold the spirits of wickedness in subjection. The human race in its entirety, as also its great social bodies, the nations and the churches, are confided to the Principalities; while the Archangels, who preside over smaller communities, seem also to have the office of transmitting to the Angels the commands of God, together with the love and light which come down even to us from the first and highest hierarchy. O the depths of the wisdom of God! Thus, then, the admirable distribution of offices among the choirs of heavenly spirits terminates in the function committed to the lowest rank, the guardianship of man, for whom the universe subsists. Such is the teaching of the School; and the apostle, in like manner, says: ‘Are they not all ministering spirits, sent to minister for them, who shall receive the inheritance of salvation?’
But God, magnificent as He is towards the whole human race, honours in a special manner the princes of His people, those who are most favoured by His grace, or who rule the earth in His name; the saints testify, that a supereminent perfection, or a higher mission in Church or State, ensures to the individual the assistance of a superior spirit, without the angel that was first deputed being necessarily removed from his charge. Moreover, with regard to the work of salvation, the Guardian Angel has no fear of being left alone at his post; at his request, and at God’s command, the troops of his blessed companions, who fill heaven and earth, are ever ready to lend him their aid. These noble spirits, acting under the eye of God whose love they desire to second by all possible means, have secret alliances between them, which sometimes induce between their clients, even on earth, unions the mystery whereof will be revealed in the light of eternity.
‘How profound a mystery,’ says Origen, ‘is the apportioning of souls to the angels destined for their guardians! It is a divine secret, part of the universal economy centred in the Man-God. Nor is it without ineffable order that the ministries of earth, the many departments of nature, are allotted to the heavenly Virtues; fountains and rivers, winds and forests, plants, living creatures of land and sea, whose various functions harmonize together by the angels directing them all to a common end.’
Again, on these words ot Jeremias: How long shall the land mourn? Origen, supported by the authority of his translator St. Jerome, continues:
It is through each one of us that the earth rejoices or mourns; and not only the earth, but water, fire, air, all the elements; by which name we must here understand not insensible matter, but the angels who are set over all things on earth. There is an angel of the land, who, with his companions, mourns over our crimes. There is an angel of the waters to whom are applied the words of the psalm: The waters saw Thee, and they were afraid, and the depths were troubled; great was the noise of the waters; the clouds sent out a sound, for Thy arrows pass.
How grand is nature viewed in this light! It is thus the ancients, more truthful as well as more poetical than our generation, always considered the universe. Their error lay in adoring these mysterious powers, to the detriment of the only God, under whom they stoop that bear up the world.
‘Air and earth and ocean, everything is full of angels,’ says St. Ambrose. ‘Eliseus, besieged by a whole army, felt no fear; for he beheld invisible cohorts assisting him. May the prophet open thine eyes also; may the enemy, be he legion, not terrify thee; thou thinkest thyself hemmed in, and thou art free: there are more with us than with them.’
But let us return to our own specially-deputed angel, and meditate on this other testimony: ‘The noble guardian of each one of us sleeps not, nor can he be deceived. Close thy door, and make the darkness of night; but remember, thou art never alone; he has no need of daylight in order to see thy actions.’ And who is it that speaks thus? Not a father of the Church, but a pagan, the slave philosopher Epictetus.
In conclusion, let us listen to the Abbot of Clairvaux, who here gives free rein to his eloquence:
In every place show respect to thy angel. Let gratitude for his benefits incite thee to honour his greatness. Love this thy future coheir, the guardian appointed for thee by the Father during thy childhood. For though we are sous of God, we are as yet but children, and long and dangerous is our journey. But God hath given His angels charge over thee, to keep thee in all thy ways. In their hands they shall bear thee up, lest thou dash thy foot against a stone. Thou shalt walk upon the asp and the basilisk; and thou shalt trample under foot the lion and the dragon. Yes; where the road is smooth enough for a child, they will content themselves with guiding thee, and sustaining thy footsteps, as one does for children. But if trials threaten to surpass thy strength, they will bear thee up in their hands. Oh those hands of angels! Thanks to them, what fearful straits we have passed through, as it were without thinking, and with no other impression left upon us, than that of a nightmare suddenly dispelled!
And in his commentary on the Canticle of canticles, St. Bernard thus describes the triumph of the angel: 'One of the companions of the Spouse, sent from heaven to the chosen soul as mediator, on witnessing the mystery accomplished, how he exults, and says: “I give thee thanks, O God of majesty, for having granted the desire of her heart!” Now it was he that, as a persevering friend, had not ceased, on the way, to murmur into the soul’s ear: “Delight in the Lord, and He will give thee the requests of thy heart;” and again: “Expect the Lord, and keep His way”; and then: “If He make any delay, wait for Him, for He will surely come and will not tarry.” Meanwhile he represented to our Lord the soul’s desire, saying: “As the hart panteth after the fountains of water, so this soul panteth after Thee, O God; have pity on her, hear her cries, and visit her in her desolation.” And now the faithful paranymph, the confidant of ineffable secrets, is not jealous. He goes from the Spouse to the bride, offering desires, bringing back gifts; he incites the one, he appeases the other. Sometimes, even in this world, he brings them into each other’s presence, either by raising up the bride in ecstasy, or by bringing down the Bridegroom; for he is one of the household, and well known in the palace; and he fears no rebuff, for every dav he beholds the face of the Father.’
Let us unite with the Church, and offer to our Guardian angels this hymn of to-day’s Vespers.
Custodes hominum psallimus angelos,
Naturæ fragili quos Pater addidit
Cadestis comites, insidiantibus
Ne succumberet hostibus.
Nam quod corruerit proditor angelus,
Concessis merito pulsus honoribus,
Ardens invidia pellere nititur
Quos cado Deus advocat.
Huc custos igitur pervigil ad vola,
Avertens patria de tibi eredita
Tam morbos animi, quam requiescere
Quidquid non sinit incolas.
Sanctæ sit Triadi laus pia jugiter,
Cujus perpetuo numine machina
Triplex hæc regitur, cujus in omnia
Regnat gloria sæcula.
We celebrate the angels, guardians of men,
whom our heavenly Father has given us as companions,
lest our weak nature should he overcome
by the snares of our enemies.
For because the traitorous angel fell,
and was justly cast down from the honours he enjoyed,
burning with envy he now endeavours
to expel those whom God calls to heaven.
Fly hither, then, O everwatchful guardian;
ward off from the land committed to thy care
as well diseases of soul, as all that threatens to disturb
the peace of the inhabitants.
May loving praise be ever to the holy Three,
by whose eternal power is ruled
this triple world, heaven and earth and the abyss;
and whose glory is supreme throughout all ages.
Before the establishment of a special feast in honour of the Guardian Angels, the following sequence was sung in certain churches on September 29.
Paranymphos summi Regis
Defensores Christi gregis vocemus suspiriis:
Montes isti circa thronum
Nuncupantur, juxta donum quod habent præ aliis.
Cœli triplex hierarchia,
Vigens sub una Sophia, trino fruens lumine:
Hæc perficit nos et purgat,
Illuminat, ut resurgat nostra mens a crimine.
Contemplantur dum accedunt,
Cum mittuntur non recedunt, intra Deum cursitant:
Hostes arcent, justos regunt,
Fovent pios quos protegunt, desolatos visitant.
Cum sint isti jam beati,
Nobis tamen deputati nostras preces deferunt:
Ut ex ipsis integrai
Possint, hisque sociari, sanctos hic non deserunt.
O quam cives hi felices,
Qui, dum expient suas vices, fruuntur perenniter:
Hos fidentes deprecemur,
Ut ab ipsis adjuvemur apud Deum jugiter.
Let us invoke with our desires the paranymphs of the most high King,
the defenders of Christ’s flock:
these are called mountains,
encircling the throne of God by a privilege all theirs.
These form the triple hierarchy of heaven,
flourishing under the one divine Wisdom, and enjoying the threefold light;
they perfect us, cleanse us,
enlighten us, that our soul may rise from sin.
They draw ever nearer to God in contemplation;
when sent to do his will, they depart not from him, for their coming and going is all within God.
They keep the enemy at bay, they guide the just,
they assist and protect their loving clients, and console them when afflicted.
Though themselves already blessed,
yet delegated to us, they carry our prayers to God:
they abandon not the saints on earth, but desire their company,
that their own ranks may be completed.
O happy citizens these! who, while fulfilling their offices,
lose not the joys of heaven:
let us pray to them with confidence,
that they may ever assist us before God.
Blessed be ye, O holy angels, for that your charity is not wearied out by the crimes of men; among so many other benefits, we thank you for keeping the earth habitable, by deigning to dwell always therein. Solitude often weighs heavily upon the hearts of God’s children, in the great towns, and in the paths of the world, where one meets only strangers or enemies; but if the number of the just grows loss, yours never diminishes. In the midst of the excited multitude, as well as in the desert, not a human being that has not beside him an angel, the representative of universal Providence over wicked and good alike. O blessed spirits! you and we have the same fatherland, the same thought, the same love; why should the confused noises of a frivolous crowd disturb the heavenly life we may lead even now with you P Does the tumult of public places hinder you from holding your choirs there, or prevent the Most High from hearing your harmonies? We also, beholding by faith the face of our heavenly Father, which you ever delightedly contemplate, we wish to sing in every place the praises of our Lord and to unite at all times our adorations with yours. Thus, when our manners have become altogether angelic, the present life will be full of peace, and we shall be well prepared for eternity.
 It has been a greater double since 1883.
 Suarez. Dc Angelis, lib. vi. cap. xviii. 5.
 Heb. i. 14.
 Origen. in Josue, Hom, xxiii.
 Jerem. xii. 4.
 Origen. in Jerem. Hom. x.juxta Hieron. viii.
 Ps. lxxvi. 17, 18.
 Job ix. 13.
 Ambr. in Psalm. Cxviii, Sermon i. 9, 11, 12.
 iv Kings vi. 16.
 Ap. Arrian. Diss, 1. 14.
 Ps. xc. 11-13.
 Bern, in Psalm, xc. Sermon xii.
 Bernard, in Cunt. Sermon xxxi.