ca. 96 A.D., Pope Saint Clement, fourth Bishop of Rome, disciple of the Apostles Peter and Paul, Letter to the Corinthians
40:1-5 Since, therefore, these things are clear to us, and we have looked into the depths of the divine knowledge, we ought to do in proper order all those things which the Master has commanded us to perform at appointed times. He has commanded the offerings and services to be celebrated, and not carelessly nor in disorder, but at fixed times and hours. He has, moreover, by His supreme will, determined where and by whom He wants them to be carried out, so that all may be done in a holy manner, according to His good pleasure and acceptable to His will. Those, then, who make their offerings at the appointed times, are acceptable and blessed; for they follow the laws of the Master and do not sin. To the high priest, indeed, proper ministrations are allotted, to the priests a proper place is appointed, and upon the levites their proper services are imposed. The layman is bound by the ordinances for the laity. …
41:2 Not everywhere, brethren, are the continual sacrifices offered, whether of petitions or in reparation for sins and trespasses, but only in Jerusalem; and even there, not in every place, but only in front of the inner temple on the altar of sacrifice; and the offering is first inspected for blemishes by the high priest and the ministers already mentioned. …
44:1-2 Our Apostles knew through our Lord Jesus Christ that there would be strife for the office of bishop. For this reason, therefore, having received perfect foreknowledge, they appointed those who have already been mentioned, and afterwards added the further provision that, if they should die, other approved men should succeed to their ministry. …
42:3-4 Receiving their instructions and being full of confidence on account of the resurrection of our Lord Jesus Christ, and confirmed in faith by the word of God, they [i.e., the Apostles] went forth in the complete assurance of the Holy Spirit, preaching the good news that the Kingdom of God is coming. Through countryside and city they preached; and they appointed their earliest converts, testing them by the Spirit, to be the bishops and deacons of future believers. …
44:4-6 Our sin will not be small if we eject from the episcopate those who blamelessly and holily have offered its Sacrifices. Blessed are those presbyters who have already finished their course, and who have obtained a fruitful and perfect release; for they have now no fear that any shall transfer them from the place to which they are appointed. For we see that in spite of their good service you have removed some from the ministry in which they served without blame.
— ca. 100 A.D., Death of Saint John, the last of the Apostles —
ca. 107 A.D., Saint Ignatius, Bishop of Antioch, Disciple of the Apostle John, Letter to the Magnesians
3:1 It becomes you not to presume on the youth of the bishop, but to show him all reverence in consideration of the authority of God the Father: just as even the holy presbyters, so I have heard, do not take advantage of his outwardly youthful appearance, but yield to him in their godly prudence: yet, not to him, but to the Father of Jesus Christ, the Bishop of all.
ca. 107 A.D., Ignatius of Antioch, Letter to the Philadelphians
9:1 Good, too, are the priests; but the high priest is better, to whom was entrusted the holy of holies; and to him alone were entrusted the secret things of God.
ca. 107 A.D., Ignatius of Antioch, Letter to the Smyrneans
— Earliest extant use of the title "Catholic Church" —
8:1 You must all follow the bishop as Jesus Christ follows the Father, and the presbytery as you would the Apostles. Reverence the deacons as you would the command of God. Let no one do anything of concern to the Church without the bishop. Let that be considered a valid Eucharist which is celebrated by the bishop, or by one to whom he appoints. 2 Wherever the bishop appears, let the people be there; just as wherever Jesus Christ is, there is the Catholic Church.
ca. 150 A.D., Saint Justin the Martyr, First Apology
66 The Apostles, in the Memoirs which they produced, which are called Gospels, have thus passed on that which was enjoined upon them: that Jesus took bread and, having given thanks, said, “Do this in remembrance of Me; this is My Body” (Lk. 22:19). And in like manner, taking the cup, and having given thanks, He said, “This is My Blood” (Matt. 26:27-28). And He imparted this to them only. …
67 On the day which is dedicated to the sun [i.e., Sunday], all those who live in the cities or who dwell in the countryside gather in a common meeting, and for as long as there is time the Memoirs of the Apostles or the writings of the prophets are read. Then, when the reader has finished, the president [i.e., one who presides at the Liturgy] verbally gives a warning and appeal for the imitation of these good examples.
Then we all rise together and offer prayers, and, as we said before, when our prayer is ended, bread is brought forward along with wine and water, and the president likewise gives thanks to the best of his ability, and the people call out their assent, saying the Amen. Then there is the distribution to each and the participation in the Eucharistic elements.
ca. 190 A.D., Saint Polycrates, Bishop of Ephesus, Letter to Pope Saint Victor of Rome
Moreover, there is also John, who reclined at the bosom of the Lord (John 13:23), and who became a priest wearing the high priest’s mitre, and a witness and a teacher. … Then there is also Polycarp in Smyrna, both bishop and martyr; and Thraseas, both bishop and martyr, from Eumenia …
— Consecrated celibacy —
And what is to be said of Sagaris, bishop and martyr …? and of Melito, the eunuch, who regulated his life entirely in the Holy Spirit, and who sleeps at Sardes … ? (Eusebius Pamphilus, History of the Church 5:24:2-5)
ca. 200, Saint Clement of Alexandria, Who Is the Rich Man That Is Saved?
42:2 After the death of the tyrant, the [Apostle John] came back again to Ephesus from the Island of Patmos; and, upon being invited, he went even to the neighboring cities of the pagans, here to appoint bishops, there to set in order whole churches, and there to ordain to the clerical estate such as were designated by the Spirit.
ca. 206 A.D., Tertullian, The Veiling of Virgins
— Ordination of women —
9 It is not permitted to a woman to speak in the church (1 Cor. 14:34-35; 1 Tim. 2:11-12); but neither (is it permitted her) to teach, nor to baptize, nor to offer, nor to claim to herself a lot in any manly function, not to say (in any) sacerdotal office.
ca. 214 A.D., Tertullian, Monogamy
— Consecrated celibacy —
8:4 Peter alone [among the Apostles] do I find married, and through mention of his mother-in-law. I presume he was a monogamist; for the Church, built upon him, would for the future appoint to every degree of orders none but monogamists. As for the rest, since I do not find them married, I must presume they were either eunuchs or continent.
ca. 215 A.D., Saint Hippolytus of Rome, Bishop of Pontus, disciple of Irenaeus, The Apostolic Tradition
3:4 [The bishop consecrating a new bishop shall pray thus, saying:] “Father ‘who knowest the hearts [of all]’ (Acts 1:24) grant upon this Thy servant whom thou hast chosen for the episcopate to feed Thy holy flock (Acts 20:28; 1 Pet. 5:2) and serve as Thine high priest, that he may minister night and day, that he may unceasingly [behold and] propitiate Thy countenance and offer to Thee the gifts of thy holy Church [i.e., the Sacraments].
3:5-6 “And that by the high priestly Spirit he may have authority ‘to forgive sins’ according to Thy command (Jn. 20:23), ‘to assign lots’ according to the authority Thou gavest to the Apostles, and that he may please Thee in meekness and a pure heart, ‘offering’ to Thee ‘a sweet-smelling savour,’ through Thy Child Jesus Christ our Lord, through Whom to Thee be glory, might and praise, to the Father and to the Son with the Holy Spirit now [and ever] and world without end. Amen.”
4:1 And when he has been made bishop let every one offer him the kiss of peace saluting him, for he has been made worthy [of this].
4:2 To him then let the deacons bring the oblation [i.e., the Eucharist] and he with all the presbyters laying his hand on the oblation shall say giving thanks. …
—Ordination of women—
11:4 Let the widow be instituted by word only and [then] let her be reckoned among the [order of] widows. But she shall not be ordained, because she does not offer the oblation nor has she a [liturgical] ministry.
11:5 But ordination is for the clergy on account of their [liturgical] ministry. But the widow is appointed for prayer, and this is [a function] of all [Christians].
ca. 217 A.D., Hippolytus, Discourse on the End of the World
41 Then He shall gather together all nations, as the holy Gospel so strikingly declares. … Come, ye hierarchs, who did me sacred service blamelessly day and night, and made the oblation of my honourable body and blood daily.
ca. 245 A.D., Origen, Homilies on Leviticus
2:4 - 3:4 [A final method of forgiveness], albeit hard and laborious [is] the remission of sins through penance, when the sinner washes his pillow in tears, when his tears are day and night his nourishment, and when he does not shrink from declaring his sins to a priest of the Lord and from seeking medicine, after the manner of him who says, “I said, ‘To the Lord I will accuse myself of my iniquity’, and you forgave the disloyalty of my heart” (Ps. 31 [32]:5). In this way there is fulfilled that too, which the Apostle James says: “If, then, there is anyone sick, let him call the presbyters of the Church, and let them impose hands upon him, anointing him with oil in the name of the Lord; and the prayer of faith will save the sick man, and if he be in sins, they shall be forgiven him” (Jas. 5:14-15).
250, Saint Cyprian, Bishop of Carthage, Letter to His Clergy
16 [9]:2 Although for lesser [i.e., venial] sins it is required that sinners do penance for a just time, after which, according to the rule of discipline, they may come to confession and, through the imposition of hands by the bishop and clergy, may receive the right of communication [i.e., Holy Communion], now, in an unpropitious time and while the persecution continues, when peace is not yet restored to the Church itself, they are being admitted to communication, and the offering [i.e., Eucharist] is made in their name; and, not yet having made a confession of sin, not yet having had hands imposed upon them by the bishop and clergy, the Eucharist is given to them, in spite of what is written: “Whoever shall eat the Bread or drink the Cup of the Lord unworthily, will be guilty of the Body and Blood of the Lord” (1 Cor. 11:27). …
18 [12]:1 Inasmuch as I find that there is not yet an opportunity of coming to you, and the Summer has already begun — a season disturbed by continual and grave illnesses — I think that we must deal with our brethren. Therefore, … if they should be seized by some misfortune or dangerous illness at a time when my return is not expected, then, before whatever presbyter is present, or if a presbyter is not found and death begins to be imminent, even before a deacon they are permitted to make their confession of sin, so that a hand may be imposed upon them in penance and they may come to the Lord with … peace.