“Our Lord Jesus Christ . . . established the worship belonging to the divine religion. . . . But the Lord desired that the sacrament of this gift should pertain to all the apostles in such a way that it might be found principally in the most blessed Peter, the highest of all the apostles. And he wanted his gifts to flow into the entire body from Peter himself, as if from the head, in such a way that anyone who had dared to separate himself from the solidarity of Peter would realize that he was himself no longer a sharer in the divine mystery. . . . [You, my brothers], must realize with us, of course, that the Apostolic See—out of reverence for it, I mean—has on countless occasions been reported to in consultation by bishops even of your own province [Vienne]. And through the appeal of various cases to this see, decisions already made have been either revoked or confirmed, as dictated by long-standing custom” -Letters 10:2–3 [A.D. 445]).

“As for the resolution of the bishops which is contrary to the Nicene decree, in union with your faithful piety, I declare it to be invalid and annul it by the authority of the holy apostle Peter” -Letters 110 (Written 445 A.D.)

“Although bishops have a common dignity, they are not all of the same rank. Even among the most blessed apostles, though they were alike in honor, there was a certain distinction of power. All were equal in being chosen [to be apostles], but it was given to one to be preeminent over the others. . . . [So today through the bishops] the care of the universal Church would converge in the one see of Peter, and nothing should ever be at odds with this head” (Letter to Anastasius of Thessalonica 14:11 (Written 446 A.D.)

Pope Leo I
“Our Lord Jesus Christ . . . has placed the principal charge on the blessed Peter, chief of all the apostles. . . . He wished him who had been received into partnership in his undivided unity to be named what he himself was, when he said: ‘You are Peter, and upon this rock I will build my Church’ [Matt. 16:18], that the building of the eternal temple might rest on Peter’s solid rock, strengthening his Church so surely that neither could human rashness assail it nor the gates of hell prevail against it” (Letters 10:1 [A.D. 445]).

Pope Leo I
“And because of the transgression of the first man, the whole stock of the human race was tainted; no one can be set free from the state of the old Adam save through Christ’s sacrament of baptism, in which there are no distinctions between the reborn, as the apostle [Paul] says, ‘For as many of you as were baptized in Christ did put on Christ; there is neither Jew nor Greek . . . ’ [Gal. 3:27–28]” (Letters 15:10[11] [A.D. 445]).

“‘Do not impose hands hastily on anyone, and be not a partner in the sins of others’ What does it mean to impose hands hastily, except to give the priestly honor to those who have not been tested, before the age of maturity, before the period of trial, before they have merits of obedience, before they have experience of discipline? And what does it mean to be a partner in the sins of others, except that the one ordaining become like the one who did not deserve to be ordained? A man may be found to be of good character and may be adorned with holy works to any degree; but he still must not rise to the rank of the diaconate or to priestly dignity or to the height of the episcopate if it is certain that he has married more than once or that his wife was previously married.”
-Letter to the Bishops of Mauretania 12:2

“It is true that the birth of the Lord according to the flesh had certain peculiarities by which it transcended the beginnings of the human condition, whether that He alone was conceived and born without concupiscence from an inviolate Virgin, or that He came from His Mother’s womb in such a way that her fruitfulness bore Him, and her virginity yet remained; but nevertheless His flesh was not of a nature different from ours. . .”
-Letter to Julian, Bishop of Kios 35:3 (Written 449 A.D.)

“For if where two or three are gathered together in His name, He says He is there in the midst of them, how much more will He not show His companionship with five hundred and twenty priests, who preferred the spread of knowledge concerning Him to their own home and affairs, when you, as the head to the members, showed your good will through those who represented you?”
-Letter of the Fathers of the Ecumenical Council of Chalcedon to Pope Leo I (Written 451 A.D.)

“Without regard to lineage and inheritance (1), the Church receives those rulers whom the Holy Spirit prepared; thus among the people of God’s adoption, the whole of which is priestly and royal, no prerogative of earthly origin can obtain the anointing, but a condescension of divine grace begets a bishop.”
-Sermon 3:1

“From the whole world only one, Peter, is chosen to preside over the calling of all nations, and over all the other Apostles, and over the Fathers of the Church. Thus, although among the people of God there are many priests and many pastors, it is really Peter who rules them all, of whom, too, it is Christ who is their chief ruler. Divine condescension, dearly beloved, has granted to this man in a wonderful and marvellous manner the aggregate of its power; and if there was something that it wanted to be his in common with other leaders, it never gave whatever it did not deny to others except through him.”
-Sermon 4:2

“Without God there is no virtue, nor does a man obtain what is proper to divinity unless he be enlivened by the Spirit of his Author. Since the Lord said to His disciples, ‘Without Me you are able to do nothing’, there is no doubt that when a man does good works he has from God both the carrying out of the work and the beginning of his will to do so.”
-Sermon 38:3

“For all things that, according to the Law, were prior, whether circumcision of the flesh, or the multitude of sacrificial victims, or the observance of the Sabbath, testified to Christ and foretold Christ’s grace. And He is the end of the Law, not by annulling but by fulfilling what is signified. For although He is the Author both of the old ways and of the new, still, He changed the sacraments of the prefigured promises, because He fulfilled the promises and put an end to announcements by His coming as the Announced. But in the area of moral precepts, no decrees of the earlier Testament are rejected; rather, in the Gospel teaching many of them are augmented, so that the things which give salvation might be more pertect and more lucid than those which promise a Savior.
-Sermon 63:5

“Participation in the Body and Blood of Christ effects nothing else but that we become that which we consume, and we carry Him everywhere both in spirit and in body, in and with whom we have died, have been buried, and have risen.”
-Sermon 63:7

“For the unchangeable Godhead of this Blessed Trinity is one in substance, undivided in operation, harmonious in will, alike in power, equal in glory. In this regard when Holy Scripture speaks in such a way that it can allot something either in deeds or in words, so that it would seem to belong to the individual Persons, Catholic Faith is not disturbed but is taught that the truth of the Trinity can be suggested to us through a peculiarity of word or operation, while the intellect must not divide what the hearing has distinguished.”
-Sermon 76:2

“When the Lord says: ‘Unless you shall have eaten the flesh of the Son of Man and drunk His blood, you shall not have life in you’, you ought to so communicate at the Sacred Table that you have no doubt whatever of the truth of the Body and Blood of Christ. For that which is taken in the mouth is what is believed in faith; and in vain do those respond, ‘Amen’, who argue against that which is received.”
-Sermon 91:3

“For we would have been unable to overcome the author of sin and death had Christ not assumed our nature and made it his own. Sin cannot defile him, nor can death hold him. For he was conceived by the Holy Spirit within the womb of a Virgin Mother, who gave birth to him without losing her virginity, just as she had remained a virgin in conceiving him.”
-Letter 28:2

“The earth of human nature was already cursed in the first liar. Only in this birth from the Blessed Virgin did it produce a blessed shoot, an exception to the vice of its roots. Its spiritual origin is acquired by anyone who is regenerated. And for every man who is born again, the water of baptism is like the virginal womb. The same Spirit that filled the Virgin now fills the baptismal font; hence, that sin, which was once removed by a holy conception, is now taken away by a mystic ablution.”
-Sermon 22:1

“By the Spirit, Christ is born from the body of his unsullied Mother; by this same Spirit, the Christian is reborn from the womb of holy Church.”
-Sermon 29:1

“He was engendered by a new kind of birth, conceived by a Virgin, born of a Virgin, without a father’s carnal concupiscence, without injuring his Mother’s integrity. Indeed, such a birth was appropriate for the future Savior of men, who, while sharing the nature of human substance, did not know the contamination of human flesh. The Author of God taking flesh is God himself, as the archangel witnesses to the Blessed Virgin Mary: ‘The Holy Spirit will come upon you, and the power of the Most High will overshadow you; hence, the holy offspring born of you will be called Son of God’ (Lk 1:35). In his origin unlike us; in his [human] nature like us- our common human customs are of no help here. It was decided by God’s almighty power that Mary should conceive as a virgin, give birth as a virgin, and remain a virgin. Do not think about the condition of his Mother, but consider the decision of the Son, who wanted in this way to be born a man and so brought it about. If you seek the truth about his nature, then recognize the matter as human; if you want to find the secret of his origin, then acknowledge the divine power. For our Lord Jesus Christ came to take away our infection, not to be infected by it; he did not come to succumb to our vices but to heal them. He came to heal the malady of our corruption and all the wounds of our scarred souls. For this reason he had to be born in a new manner, since he was bringing the new grace of spotless integrity to our human bodies. He had to keep his Mother’s original virginity intact, and it was necessary that the power of the holy Spirit should safeguard the defense of her modesty, which he was pleased to call the dwelling place of holiness.
For he had decided to raise up what was fallen and restore what was broken apart and to strengthen purity for overcoming the seductons of the flesh, so that virginity, which in others cannot be preserved after childbirth, might be imitated even by others, in rebirth.
-Leo the Great, Sermo 22, 2; PL $4, 195-96