From Dom Guéranger's The Liturgical Year.
ALTHOUGH amongst the saints there is none who is undeserving of earth's humble homage, or whose intercession is powerless on our behalf, yet the cultus rendered to them, and the confidence evinced, necessarily vary in proportion to what we know of their glory. It is therefore only just, as St Leo remarks in to-day’s Office, that we should honour in a most special manner those whom divine grace has exalted so far above all others, that they are considered, as it were, the two brilliant eyes of Christ’s mystical body, the Church, giving light to all of us, who are the members thereof. For this reason, the festival of these two princes of the apostles is held superior to that of any other servant of God occurring in the entire cycle.
When the Church’s own practice gave tone to the particular customs of the various countries, national confidence and even private devotion knew no other preferences than those of the holy liturgy; and long were it to tell of all that can be produced by history, public charts, simple contracts and monuments of every sort, in endless proof of our forefathers' love for the glorious doorkeeper of heaven and his illustrious companion armed with the sword. Faith was lively in those days. It was then well understood that of all God's gifts to earth, none is comparable to the graces of sanctification, doctrine and unity, of which Peter and Paul are for all the predestined instruments. The heart became dilated as the mind expanded. Men were eager, therefore, to know as much as they could touching the lives of these fathers of the Christian people; and they made great account of the devotedness wherewith the two apostles had so unsparingly poured out their sweat and blood for them.
Alas! can it be said that such is the case nowadays? How many baptized persons are there, Catholics not merely in name, but even considered practical Catholics, who scarcely possess such elementary notions of true Christianity as to appreciate the importance of the role performed amongst men by these founders of the Church, or even to give it a passing thought! Yet some there are, and thanks be to God their number is now on the increase, who glory in studying the principles on which rests the divine constitution of society purchased by the Blood of our Lord. Such men as these understand and revere the august position which has been, and always must be, held by Peter and Paul in the economy of Christian dogma. Nevertheless, do even these persons honour really as they ought these two princes of the apostles? What they know on this subject shows them plainly enough that it cannot be the case with these two apostles as it is with many other saints, whose cultus increases or diminishes according to circumstances of time, place and the like: the cultus of SS Peter and Paul has its roots in the very foundations of Catholicism; whether in nations or in individual souls it cannot wane, save to the great detriment of Catholicity itself. But then, no cultus is real, except that which implies devotion and love; can it be really said of the class of persons to whom we refer that their knowledge of the holy apostles has penetrated deeply enough from their mind into their heart?
In the case of too many people, this knowledge, being confined to the region of theory, is not sufficiently personal with regard to the two apostles themselves; and, therefore, principles the most nicely drawn do by no means impart the spirit of faith, the seat of which is in the heart, and which animates the life. Let them put the finishing stroke to their science. Without losing sight of dog matic science, let them seek in prayer and in humble study of the Gospel of the Acts of the Apostles, of the Epistles and of ecclesiastical tradition, that intimate revelation of the very soul of Peter and of Paul which cannot fail to make them admire, and above all love them personally as much as and even more than their sublime prerogatives. Then perhaps will they be astonished to have come so late to a knowledge of many precious details and thousands of instructive features about them, which little children in bygone ages (now reputed barbarous) would have blushed not to know. As a necessary consequence, they will thus begin to feel more Catholic in soul; they will consider themselves happy to have learnt, at last, how to share the devotion of the humble peasant woman and her ingenuous confidence, not unmixed with fear, in the doorkeeper of paradise.
The following beautiful Preface is taken from the Mozarabic Missal. Its theme is that assemblage of divine contrasts, amidst which eternal Wisdom loves, as it were, to play, and which are found wonderfully multiplied in the lives of these two apostles.
Dignum et justum est, omnipotens Pater, nos tibi ingentes agere gratias pro multiplici apostolomm Petri et Pauli gloria: quam eis per diversas munerum distributiones larga satis pietate donasti. Quos et Unigeniti tui discipulos: et gentium fecisti esse magistros. Qui ob Evangelii prædicationem quum cœlorum præficiantur in regnis: carcerum clauduntur angustiis. Potestatem accipiunt peccata solvendi: et ferri vinculis alligantur. Sanitatem donant: et ægritudines portant. Dæmonibus imperant: et ab hominibus flagellantur. Mortes fugant: et fugiunt persequentes. Super mare ambulant: et in labore desudant. Montes verbo transferunt: et propriis victum manibus quærunt. Judicaturi angelos: in quæstionem mittuntur. Cum Deo vivunt: in mundo periclitantur. Postremo Christus eis serviens pedes lavat: et facies eorum blasphemantium manus alapis colaphizat. Nihil sustinentibus pene defuit ad tolerantiam: nihil superantibus victoriæ non adfuit ad coronam. Si recurramus quot ad testificandam fidei veritatem ærumnarum pertulerint in tormentis frequenter suis i superfuere martyribus. Si in mirabilibus, hoc per Christum fecere quod Christus: si in passionibus, hoc sustinuerunt illi necessitate mortali quod ille voluntate moriendi. Isti ejus viribus: ille suis. Probantes doctrinæ auctoritatem similitudine: non asqualitate doctoris.
Implevit Petrus suo tempore: quod promiserat ante tempus. Posuit animam suam pro illo: quem se non crediderat negaturum. Quia ad arduæ sponsionis celeritatem nimia charitate præventus, non intellexit servum pro Domino dare non posse quod pro servo ante Dominus non dedisset: similiter non renuit crucifigi, sed æqualiter non præsumpsit appendi. Obiit ille rectus: iste subjectus. Ille ut majestatem ascendentis sublimitate proferret: iste ut fragilitatem descendentis humilitate monstraret.
Nec Paulus affectu minor, meminit quem sibi arrogaverat dicens: Mihi vivere Christus est, et mori lucrum. Gaudet, insanientis ictibus percussoris, domitas jugo Christo offerre cervices; et pro corporis sui capite, dare corporis sui caput. Diviserunt sibi passionis dominicæ vestimentum duo milities Dei: unus in patibulo, alter in gladio; Petrus in transfixione, Paulus in sanguine.
His igitur dispari mortis genere, non dispari moriendi amore perfunctis: exsultet in eorum doctrinis Ecclesia catholica; in exsequiis religiositas universa; in memoriis urbs Romana; in patrociniis omnis anima christiana. Hæc autem omnia tu, Domine, operaris: qui a prophetis demonstraris; ab angelis adoraris; et in omni sæculo apostolorum lumine declararis. Cui merito omnes Angeli et Archangeli non cessant clamare quotidie, ita dicentes: Sanctus, Sanctus, Sanctus.
It is truly meet and just, O almighty Father, that we render our deepest thanks unto thee for the multiplied glory of thine apostles Peter and Paul, which thou hast by divers distribution of gifts largely bestowed upon them, of thine immense goodness. Thou hast made them to be disciples of thine only-begotten Son and teachers of the Gentiles. On account of their preaching of the Gospel, though they are first in the heavenly kingdom, yet are they shut up in strait prisons. They receive power to absolve sins: yet are they enthralled in chains of iron. They give health; and they endure bitter anguish. They command demons; and they are scourged by men. They drive away death; and they themselves flee from the face of persecutors. They walk upon the waters; and sweat with toil. By their word are mountains removed; and by the labour of their own hands they earn their bread. They are appointed judges of angels; and they are put to the torture. With God they live; in the world they are in peril. Finally, Christ ministering unto them washes their feet; and by the hands of blasphemers are their faces buffeted with blows. Scarce anything was wanting of sufferings unto their endurance; nor is anything now wanting to the crown of victory in their triumph. If we go over all that they suffered in their torments, they outstrip the martyrs. If we look into their miracles, we see that they did the same by Christ as Christ himself did: if we consider their passion, we behold that they endured by mortal necessity that which he did by voluntary death; but they by his strength, he by his own. Proving the authority of their doctrine by their likeness to their teacher, not by their equality with him.
Peter accomplished in due time that which he promised before his time. He laid down his life for him whom he believed that he would never deny. Since in the burning impetuosity of his great love, he had not understood that the servant cannot give to his Lord that which his Lord hath not as yet given for the servant; so in like manner he refused not, when the time came, to be crucified; but he presumed not to hang in the same position as his Lord. The One died upraised, the other placed downwards: the One thus declared his majesty ascending on high; the other thus showed his fragility that tends unto earth.
Nor in less affection doth Paul remember that which he said of himself: Christ is my life, and to die is my gain. Glad is he, beneath the stroke of the raging murderer, to offer unto Christ a neck tamed to the yoke; and for the true Head of the body, to give the mortal head of his own body. Lo! these two soldiers of God, how they divide betwixt them the garment of the Lord’s Passion; the one on the gibbet, the other beneath the sword; Peter in transfixion, Paul in bloodshedding.
These two, therefore, differ in the manner of their death, but not in the love shown forth in dying: the Catholic Church exults in their teaching; all religion, in the celebration of their death; the Roman city, in their memory; each Christian soul, in their patronage. Now, all these things thou, O Lord, hast operated, thou who wast pointed out by the prophets, art adored by the angels, art manifested throughout the world, by the light of the apostles. To whom meetly, all Angels and Archangels unceasingly cry out daily, saying: Holy, Holy, Holy.
The same liturgy makes use of the following hymn on this festival. It is attributed, not without some foundation, to St Ambrose, and seems to have preceded the hymn of Elpis in liturgical use.
Diem sacravit sæculis,
Petri triumphum nobilem,
Pauli coronam proferens.
Conjunxit æquales viros
Cruor triumphalis necis;
Deum secutos præsules
Christi coronavit fides.
Primus Petrus apostolus;
Nec Paulus impar gratia:
Electionis vas sacræ
Petri adæquavit fidem.
Verso crucis vestigio,
Simon honorem dans Deo,
Suspensus ascendit, dati
Non immemor oraculi.
Præcinctus, ut dictum est, senex,
Elevatus ab altero,
Quo nollet ivit, sed volens
Mortem subegit asperam.
Hinc Roma celsum verticem
Fundata tali sanguine
Et vate tanto nobilis.
Tantas per Urbis ambitum
Stipata tendunt agmina:
Trinis celebratur viis
Festum sacrorum martyrum.
Prodire quis mundum putet,
Concurrere plebem poli:
Electa genitum caput,
Sedes magiatri gentium.
Deo Patri sit gloria,
Ejusque soli Filio,
Cum Spiritu Paraclito
In sempiterna sæcula.
The apostles’ passion
hath consecrated this immortal day,
presenting Peter's noble triumph
and Paul's crown.
The gore of their victorious death
hath conjoined these men, peers in fame;
the faith of Christ hath crowned
these jubilant followers of God.
The first, Peter the apostle;
next, Paul his peer in grace.
The vessel of sacred election
hath equalled the faith of Peter.
Not unmindful of the oracle,
Simon, suspended, ascends
along the heaven-turned footprints
of the cross, giving glory to God.
Even as was foretold, the old man,
girded by another’s hand, is upraised.
Whither he would not, he has had to go;
but willing now, dire death hath he subdued.
Hence Rome hath become
the exalted head of religious worship,
founded, as she is, in such blood as this,
and by so illustrious a prophet.
Through all the vast extent
of so great a city, close packed,
crowds are pressing along, by three ways,
for the celebration of the holy martyrs' festival.
It might be supposed that the whole world had come forth,
that the people of all nations had assembled here;
lo! verily, the chosen head of the Gentiles,
the seat of the teacher of the Gentiles!
Glory be to God the Father,
and to his only Son,
together with the Paraclete Spirit,
for ever and ever.
 Sermo I in Nat. A post. Lect. II Nocturni.