“It might not be surprising that the use of a virgin-mother as an image of the Church began to be paralleled at this time by the use of Mary, virgin and mother, for the same purpose. Preceded by Ephrem in the East, Ambrose was the first to develop this metaphor in the West, and in an important passage he does so in terms that recall his virgin-mother-Church metaphor. After recounting the relationship between Mary and Joseph as recorded in the Gospel of Luke, he comments on its deeper meaning:
Let us address the mystery: She was truly espoused, but a virgin, because she is a type of the Church, which is immaculate but married. As a virgin she begot us form the Spirit, as a virgin she bears us without groaning. And this is perhaps why the holy Mary, although married to one person, was impregnated by another, because the individual churches as well are in fact filled with the Spirit and with grace, while simultaneously being joined under the aegis of a temporal priest.
(Boniface Ramsey, Beginning to Read the Fathers, pp. 112-113)