Thomas Aquinas

“ Consequently, just as it was possible for the first man to be produced, by the Divine power, "from the slime of the earth," so too was it possible for Christ's body to be made, by Divine power, from a virgin without the seed of the male.
Reply to Objection 5: According to the Philosopher (De Gener. Animal. i, ii, iv) , in conception the seed of the male is not by way of matter, but by way of agent: and the female alone supplies the matter. Wherefore though the seed of the male was lacking in Christ's conception, it does not follow that due matter was lacking. ”

“ This argument is true of those things which come into existence by the way of nature: since nature, just as it is fixed to one particular effect, so it is determinate to one mode of producing that effect. ”

“ Wherefore it is unfitting that in His Birth He should corrupt His Mother's virginity. Thus Augustine says in a sermon on the Nativity of Our Lord: "It was not right that He who came to heal corruption, should by His advent violate integrity."
Thirdly, it was fitting that He Who commanded us to honor our father and mother should not in His Birth lessen the honor due to His Mother.
Reply to Objection 1: Ambrose says this in expounding the evangelist's quotation from the Law: "Every male opening the womb shall be called holy to the Lord." ”