Gregory of Nyssa
Catena Aurea · Lukasevangelium 1
Then said Mary unto the angel, How shall this be, seeing I know not a man? And the angel answered and said unto her, The Holy Ghost shall come upon thee, and the power of the Highest shall overshadow thee: therefore also that holy thing which shall be born of thee shall be called the Son of God.
(sup.) These words of Mary are a token of what she was pondering in the secrets of her heart; for if for the sake of the marriage union she had wished to be espoused to Joseph, why was she seized with astonishment when the conception was made known unto her? seeing in truth she might herself be expecting at the time to become a mother according to the law of nature. But because it was meet that her body being presented to God as an holy offering-should be kept inviolate, therefore she says, Seeing that I know not a man. As if she said, Notwithstanding that thou who speakest art an Angel, yet that I should know a man is plainly an impossible thing. How then can I be a mother, having no husband? For Joseph I have acknowledged as my betrothed.