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.
(Orat. in Diem Nat.) Or he says, overshadow thee, because as a shadow takes its shape from the character of those bodies which go before it, so the signs of the Son’s Deity will appear from the power of the Father. (non occ. in Greg. Nyss.). For as in us a certain life-giving power is seen in the material substance, by which man is formed; so in the Virgin, has the power of the Highest in like manner, by the life-giving Spirit, taken from the Virgin’s body a fleshly substance inherent in the body to form a new man. Hence it follows, Therefore also that holy thing which shall be born of thee.