The following citations complied by William Albrecht.
Protoevangelium of James
“And when she was twelve years old there was held a council of priests, saying, ‘Behold, Mary has reached the age of twelve years in the temple of the Lord. What then shall we do with her, lest perchance she defile the sanctuary of the Lord?’ And they said to the high priest, ‘You stand by the altar of the Lord; go in and pray concerning her, and whatever the Lord shall manifest to you, that also will we do.’ . . . [A]nd he prayed concerning her, and behold, an angel of the Lord stood by him saying, ‘Zechariah! Zechariah! Go out and assemble the widowers of the people and let them bring each his rod, and to whomsoever the Lord shall show a sign, his wife shall she be. . . . And Joseph [was chosen]. . . . And the priest said to Joseph, ‘You have been chosen by lot to take into your keeping the Virgin of the Lord.’ But Joseph refused, saying, ‘I have children, and I am an old man, and she is a young girl’” (8–9).
“And Annas the scribe came to him [Joseph] . . . and saw that Mary was with child. And he ran away to the priest and said to him, ‘Joseph, whom you did vouch for, has committed a grievous crime.’ And the priest said, ‘How so?’ And he said, ‘He has defiled the virgin whom he received out of the temple of the Lord and has married her by stealth’” (ibid., 15).
“And the priest said, ‘Mary, why have you done this? And why have you brought your soul low and forgotten the Lord your God?’ . . . And she wept bitterly saying, ‘As the Lord my God lives, I am pure before him, and know not man’” (ibid.).[A.D. 150].
Clement of Alexandria
For some say that, after she brought forth, she was found, when examined, to be a virgin.
Now such to us are the Scriptures of the Lord, which gave birth to the truth and continue virgin, in the concealment of the mysteries of the truth.
Stromata Book 7 Chapter 16 [A.D. 198]
Gregory the Wonder-Worker
The Holy Virgin is herself both an honourable temple of God and a shrine made pure, and a golden altar of whole burnt offerings. By reason of her surpassing purity [she is] the Divine incense of oblation ( = προθέσεως),and oil of the holy grace, and a precious vase bearing in itself the true nard; [yea and] the priestly diadem revealing the good pleasure of God, whom she alone approacheth holy in body and soul. [She is] the door which looks eastward, and by the comings in and goings forth the whole earth is illuminated. The fertile olive from which the Holy Spirit took the fleshly slip (or twig) of the Lord, and saved the suffering race of men. She is the boast of virgins, and the joy of mothers; the declaration of archangels, even as it was spoken: “Be thou glad and rejoice, the Lord with thee”; and again, “from thee”; in order that He may make new once more the dead through sin.
Thou didst allow her to remain a virgin, and wast pleased, O Lord, to lie in the Virgin’s womb, sending in advance the archangel to announce it [to her]. But he from above, from the ineffable hosts, came unto Mary, and first heralded to her the tidings: “Be thou glad and rejoice.” And he also added, “The Lord with thee. Blessed art thou among women, and blessed is the fruit of thy womb.” But she was in tumult, and pondered in her mind what sort of tidings was this. But then in seemly fashion, I ween, the grace chose out the Holy Virgin; for she was wise in all ways, nor was there her like among women of all nations.
- The Virgin spake in turn unto the angel: My mind swims in thy words as in a sea. How shall this be unto me? for I desire not to know an earthly man, because I have devoted myself to the heavenly Bridegroom. I desire to remain a virgin. I wish not to betray the honour of my virginity.
- Again in such words as these the angel confirmed the holy Virgin: Fear not, Mary. For ’tis not to frighten thee I came, but to dispel all thought of fear. Fear not, Mary; for thou hast found grace at God’s hands. Scan not too narrowly the grace, since it deigns not to give way to the laws of nature. The Holy Spirit shall come unto thee; wherefore that which is born of thee is holy and Son of God, sharer of the form and sharer of the substance, and sharer of the eternity of the Father; in whom the Father, having acquired all manifestations, hath the adumbration (? of Himself) face to face,4and by means of the light the glory gleameth forth.
-The Homily of St. Gregory the Wonder-worker, concerning the Holy Mother of God, ever-virgin(Mid 200s)
Origen of Alexandria
“The Book [the Protoevangelium] of James [records] that the brethren of Jesus were sons of Joseph by a former wife, whom he married before Mary. Now those who say so wish to preserve the honor of Mary in virginity to the end, so that body of hers which was appointed to minister to the Word . . . might not know intercourse with a man after the Holy Spirit came into her and the power from on high overshadowed her. And I think it in harmony with reason that Jesus was the first fruit among men of the purity which consists in [perpetual] chastity, and Mary was among women. For it were not pious to ascribe to any other than to her the first fruit of virginity” (Commentary on Matthew 2:17 [A.D. 248]).
Ephrem the Syrian
Lo, a Virgin is become a Mother, preserving virginity with its seals unbroken…She is made God’s Mother and is at the same time a servant, and the work of His wisdom…(24) In Eden Eve became a debtor, and the debt whereby her posterity in their generation were doomed to death was written in letters large. The Serpent, that wicked scrivener, wrote it out, signed and gave it force with the seal of his fraud….(26) Eve was a debtor to sin. But for Mary the debt was reserved that the daughter might pay her mother’s debts and tear up the handwriting that was handed on her mother’s tears as a legacy to all generations…(30) Since Mary was the Virgin inviolate – prefigured by the blest land of Eden before its surface was torn by furrows — there blossomed from her bosom the Tree of Life, the taste of which…gives life to souls….”Hymns on the Blessed Mary 18 [A.D. 330]
Hilary of Poitiers
“If they [the brethren of the Lord] had been Mary’s sons and not those taken from Joseph’s former marriage, she would never have been given over in the moment of the passion [crucifixion] to the apostle John as his mother, the Lord saying to each, ‘Woman, behold your son,’ and to John, ‘Behold your mother’ [John 19:26–27), as he bequeathed filial love to a disciple as a consolation to the one desolate” (Commentary on Matthew 1:4 [A.D. 354]).
“Let those, therefore, who deny that the Son is by nature from the Father and proper to his essence deny also that he took true human flesh from the ever-virgin Mary” (Discourses Against the Arians 2:70 [A.D. 360]).
Basil the Great
“Mary’s virginity was necessary until the service of the Incarnation, and what happened afterward need not be investigated in order to affect the doctrine of the mystery. The lovers of Christ [that is, the faithful] do not allow themselves to hear that the Mother of God ceased at a given moment to be a virgin, we consider their testimony sufficient.”
“Mary the Perpetual(Ever) Virgin”
On the Generation of Christ [A.D. 365]
Gregory of Nyssa
“And what did Mary do? Listen to the pure virgin’s utterance. The angel declared the birth, and she clings to her virginity, judging incorruption to be nobler than the angelic appearance and could neither disbelieve the angel nor abandon her judgments. She says, I have no experience of intercourse with a husband: “How will this happen to me, since  I have not known a husband?”
Oration on the Savior’s Nativity [A.D. 370]
Epiphanius of Salamis
“We believe in one God, the Father almighty, maker of all things, both visible and invisible; and in one Lord Jesus Christ, the Son of God . . . who for us men and for our salvation came down and took flesh, that is, was born perfectly of the holy ever-virgin Mary by the Holy Spirit” (The Man Well-Anchored 120 [A.D. 374]).
“And to holy Mary, [the title] ‘Virgin’ is invariably added, for that holy woman remains undefiled” (Medicine Chest Against All Heresies 78:6 [A.D. 375]).
“[Helvidius] produces Tertullian as a witness [to his view] and quotes Victorinus, bishop of Petavium. Of Tertullian, I say no more than that he did not belong to the Church. But as regards Victorinus, I assert what has already been proven from the gospel—that he [Victorinus] spoke of the brethren of the Lord not as being sons of Mary but brethren in the sense I have explained, that is to say, brethren in point of kinship, not by nature. [By discussing such things we] are . . . following the tiny streams of opinion. Might I not array against you the whole series of ancient writers? Ignatius, Polycarp, Irenaeus, Justin Martyr, and many other apostolic and eloquent men, who against [the heretics] Ebion, Theodotus of Byzantium, and Valentinus, held these same views and wrote volumes replete with wisdom. If you had ever read what they wrote, you would be a wiser man” (Against Helvidius: The Perpetual Virginity of Mary 19 [A.D. 383]).
“You [Helvidius] say that Mary did not remain a virgin. As for myself, I claim that Joseph himself was a virgin, through Mary, so that a virgin Son might be born of a virginal wedlock” (ibid., 21).
Thus, what it was necessary for thee to learn of Him, this He Himself hath said; that the Virgin was untouched by man until the birth; but that which both was seen to be a consequence of the former statement, and was acknowledged, this in its turn he leaves for thee to perceive; namely, that not even after this, she having so become a mother, and having been counted worthy of a new sort of travail, and a child-bearing so strange, could that righteous man ever have endured to know her. For if he had known her, and had kept her in the place of a wife, how is it that our Lord commits her, as unprotected, and having no one, to His disciple, and commands him to take her to his own home?
GOSPEL OF MATTHEW HOMILY 5:3 [A.D. 385]
Didymus the Blind
“It helps us to understand the terms ‘first-born’ and ‘only-begotten’ when the Evangelist tells that Mary remained a virgin ‘until she brought forth her first-born son’ [Matt. 1:25]; for neither did Mary, who is to be honored and praised above all others, marry anyone else, nor did she ever become the Mother of anyone else, but even after childbirth she remained always and forever an immaculate virgin” (The Trinity 3:4 [A.D. 386]).
Ambrose of Milan
“Imitate her [Mary], holy mothers, who in her only dearly beloved Son set forth so great an example of material virtue; for neither have you sweeter children [than Jesus], nor did the Virgin seek the consolation of being able to bear another son” (Letters 63:111 [A.D. 388]).
“In being born of a Virgin who chose to remain a Virgin even before she knew who was to be born of her, Christ wanted to approve virginity rather than to impose it. And he wanted virginity to be of free choice even in that woman in whom he took upon himself the form of a slave” (Holy Virginity 4:4 [A.D. 401]).
“It was not the visible sun, but its invisible Creator who consecrated this day for us, when the Virgin Mother, fertile of womb and integral in her virginity, brought him forth, made visible for us, by whom, when he was invisible, she too was created. A Virgin conceiving, a Virgin bearing, a Virgin pregnant, a Virgin bringing forth, a Virgin perpetual. Why do you wonder at this, O man?” (Sermons 186:1 [A.D. 411]).
Cyril of Alexandria
“[T]he Word himself, coming into the Blessed Virgin herself, assumed for himself his own temple from the substance of the Virgin and came forth from her a man in all that could be externally discerned, while interiorly he was true God. Therefore he kept his Mother a virgin even after her childbearing” (Against Those Who Do Not Wish to Confess That the Holy Virgin is the Mother of God 4 [A.D. 430]).
“Where are they who think that the Virgin’s conception and giving birth to her child are to be likened to those of other women? For, this latter case is one of the earth, and the Virgin’s is one from heaven. The one case is a case of divine power; the other of human weakness. The one case occurs in a body subject to passion; the other in the tranquility of the divine Spirit and peace of the human body. The blood was still, and the flesh astonished; her members were put at rest, and her entire womb was quiescent during the visit of the Holy One, until the Author of flesh could take on His garment of flesh, and until He, who was not merely to restore the earth to man but also to give him heaven, could become a heavenly Man. The virgin conceives, the Virgin brings forth her child, and she remains a virgin.”
Sermon 117,(A.D. 432),in FC,XVII,200
Pope Leo I
“His [Christ’s] origin is different, but his [human] nature is the same. Human usage and custom were lacking, but by divine power a Virgin conceived, a Virgin bore, and Virgin she remained” (Sermons 22:2 [A.D. 450]).
The Tome of Leo (one of the most important documents in Church History)
“And then he would not speak so erroneously as to say that the Word became flesh in such a way that Christ, born of the Virgin’s womb, had the form of man, but had not the reality of His mother’s body. Or is it possible that he thought our Lord Jesus Christ was not of our nature for this reason, that the angel, who was sent to the blessed Mary ever Virgin, says, The Holy Ghost shall come upon you and the power of the Most High shall overshadow you: and therefore that Holy Thing also that shall be born of you shall be called the Son of God.”
NOTE: Leo’s Tome was read at the Council of Chalcedon as a mark of orthodoxy.