Ancient Christian Thought on Mary's Spiritual Motherhood

Then he said to the disciple, “Here is your mother.” And from that hour the disciple took her into his own home.

John 19:27

Contrary to certain assertions, there was in fact an understanding in the early Church of Mary being a spiritual mother to Christians, albeit, they do not convey the full blossoming of Marian devotion as we have it today. What they do convey, however, is the idea that Mary, by virtue of having birthed the Redeemer, has by extension, also birthed all the redeemed.

For the most part, it is conveyed in a formal, theological sense, and not in the personal, devotional sense of "Mama Mary." But this is somewhat expected: the earliest writings of the Church are almost all focused either on apologetics against heresy and paganism, or on church discipline. Theology for theology's sake was not the standard for most of the ancient saints, and any purely sentimental expression of devotion was all the more infrequent. So the fact that this concept of the Blessed Virgin being a universal mother to the members of Christ's body is present at all is noteworthy, and in my mind, can be argued to supply enough substance for adequate development of later ages.

First Century*:

And a great portent appeared in heaven, a woman clothed with the sun, with the moon under her feet, and on her head a crown of twelve stars; she was with child and she cried out in her pangs of birth, in anguish for delivery. And another portent appeared in heaven; behold, a great red dragon, with seven heads and ten horns, and seven diadems upon his heads. His tail swept down a third of the stars of heaven, and cast them to the earth. And the dragon stood before the woman who was about to bear a child, that he might devour her child when she brought it forth; she brought forth a male child, one who is to rule all the nations with a rod of iron, but her child was caught up to God and to his throne, and the woman fled into the wilderness... Then the dragon was angry with the woman, and went off to make war on the rest of her offspring, on those who keep the commandments of God and bear testimony to Jesus.-St. John, The Revelation of Jesus Christ to the His Servant John, c. 90

Second Century:

Again, there are those who say, He is a man, and who shall know him? and, I came unto the prophetess, and she bore a son, and His name is called Wonderful, Counsellor, the Mighty God; and those [of them] who proclaimed Him as Immanuel, [born] of the Virgin, exhibited the union of the Word of God with His own workmanship, [declaring] that the Word should become flesh, and the Son of God the Son of man (the pure One opening purely that pure womb which regenerates men unto God, and which He Himself made pure)
-St. Irenaeus of Lyons, Against Heresies IV:33:11

Third Century:

We may therefore make bold to say that the Gospels are the first fruits of all the Scriptures, but that of the Gospels that of John is the first fruits. No one can apprehend the meaning of it except he have lain on Jesus' breast and received from Jesus Mary to be his mother also. Such an one must he become who is to be another John, and to have shown to him, like John, by Jesus Himself Jesus as He is. For if Mary, as those declare who with sound mind extol her, had no other son but Jesus, and yet Jesus says to His mother, "Woman, behold your son,"(John 19:26) and not "Behold you have this son also", then He virtually said to her, "Lo, this is Jesus, whom you bore." Is it not the case that every one who is perfect lives himself no longer, (Galatians 2:20) but Christ lives in him; and if Christ lives in him, then it is said of him to Mary, "Behold your son Christ."
-Origen of Alexandria, Commentary on the Gospel of John, I:6

Fourth Century: 

“Hail, full of grace, the Lord is with you” (Lk 1:28). This is she who was prefigured by Eve and who symbolically received the title of mother of the living (cf. Gen 3:20). For Eve was called mother of the living after she had heard the words, “You are dust and to dust you shall return” (Gen 3:19), in other words, after the fall. It seems odd that she should receive such a grand title after having sinned. Looking at the matter from the outside, one notices that Eve is the one from whom the entire human race took its origin on this earth. Mary, on the contrary, truly introduced life itself into the world by giving birth to the Living One, so that Mary has become the Mother of the living.
-St. Epiphanius of Salamis, Panarion (Against Heresies) 78:18 (emphasis mine)

Fifth Century:

His mother is [a figure of] the whole Church, because she herself assuredly gives birth to His members, that is, His faithful ones... that one female, not only in the Spirit, but also in the flesh, is both a mother and a virgin. And a mother indeed in the Spirit, not of our Head, Which is the Saviour Himself, of Whom rather she was born after the Spirit: forasmuch as all, who have believed in Him, among whom is herself also, are rightly called children of the Bridegroom: but clearly the mother of His members, which are we: in that she wrought together by charity, that faithful ones should be born in the Church, who are members of That Head: but in the flesh, the mother of the Head Himself.
-St. Augustine of Hippo, On Holy Virginity 5, 6

Notable in all these expressions, they carry a Christological significance. Jesus Christ is the connection between Mary and all those who think of her as their mother, and that any Marian devotion practiced by Christians will be depraved if devotion to Christ is not its means and its end.