31 Let us remember these things, brethren: let us use these weapons in our defence. Let us not endure those heretics who teach Christ's coming as a phantom. Let us abhor those also who say that the Saviour's birth was of husband and wife; who have dared to say that He was the child of Joseph and Mary, because it is written, And he took unto him his wife. For let us remember Jacob who before he received Rachel, said to Laban, Give me my wife. For as she before the wedded state, merely because there was a promise, was called the wife of Jacob, so also Mary, because she had been betrothed, was called the wife of Joseph.
Mark also the accuracy of the Gospel, saying, And in the sixth month the Angel Gabriel was sent from God unto a city of Galilee, named Nazareth, to a virgin espoused to a man whose name was Joseph, and so forth. And again when the census took place, and Joseph went up to enrol himself, what says the Scripture? And Joseph also went up from Galilee, to enrol himself with Mary who was espoused to him, being great with child. For though she was with child, yet it said not “with his wife,” but with her who was espoused to him.
For God sent forth His Son, says Paul, not made of a man and a woman, but made of a woman only, that is of a virgin. For that the virgin also is called a woman, we showed before. For He who makes souls virgin, was born of a Virgin.
Source: Catechetical Lectures (New Advent)