The holy Gospel, the word of God given to men, tells us in a passage often taken up in the liturgy: “Behold, you will conceive in your womb, and you will give birth to a son, and you will call his name Jesus.” (Lk. 1:31).
These words forcefully affirm to us that human nature, that the Word united to be embodied, was conceived by the Virgin Mary. Everywhere the Gospel speaks of Mary as the mother of Jesus. And for St. Joseph, the sacred text makes a difference and specifies: “Jesus was, as we believed, the son of Joseph” (Lk 3:23).
Some heretics, such as the Docets or the Valentinians, denied the reality of the human nature of Jesus, and therefore the motherhood of Mary. These people say that the body of Jesus is of heavenly origin and only passed through Mary.
But Tradition and the teaching of the popes have always asserted that the words of the Gospel should be taken strictly.
This is how the symbol (Credo) of St. Athanasius affirms this teaching: “(Christ) is man, from the flesh of his mother, born in time.”
This truth is repeated over and over in all the symbols of antiquity. One of the best known, the Apostle’s Creed, says that “Christ was born of the Virgin Mary.”
St. Leo the Great, in his Tome to Flavien, insists on this aspect:
But we must not understand this new and unique generation, in the sense that its novelty makes it foreign to the motherhood of other mothers. Because although it is the Holy Spirit who gave fertility to the Virgin, nevertheless it is a real body which was conceived of her body: ‘the Word was made flesh and he dwelt in us’ (Jn. 1:14); which means: in this flesh which He drew from man and which He animated with the breath of rational life.
The truth of the body of Christ, that is, of his humanity, is linked to the motherhood of Mary. If the Virgin did not give this body to her divine Son, then he is not really a man. The Word did not really incarnate.
This is why the Fathers insist on this notion of the “true body of Christ” in connection with the Mother of God. We this by singing the Ave verum: “Ave verum corpus natum de Maria Virgine – Hail, true Body born of the Virgin Mary.”
It must therefore be affirmed that, in the conception of Jesus, Mary brought everything that a mother brings in the natural process of motherhood. This is what the phrase “Mary is the mother of Jesus” means.
She provides the material that will be the human body of Christ. Theologians use the term ministerial cause. This means “at the service of”, as a minister or a servant is at the service of his master.
The Most Holy Virgin is at the service of the Incarnation of the Word. She also said very explicitly at the Annunciation: “Ecce ancilla Domini – Here is the handmaid of the Lord.”
It should be noted carefully, however, in the case of the human generation of Christ, that two facts appear which are known to us only by faith alone: this motherhood is virginal and the Son who is born of the Virgin is God.
It is from this human generation, from this motherhood of the Virgin who engenders the holy humanity of Christ, that divine motherhood flows. It is because Mary is the mother of the body of her Son that she can be called Mother of God. The two aspects are intrinsically linked.