Jesus who lived for thirty years at Nazareth in Galilee, is the eternal Son of God was conceived by the power of the Holy Spirit and born of the Virgin Mary, a daughter of Adam.

This faith is presented in the Letter of St. Paul to the Galatians, "When the time had fully come, God sent forth his Son, born of woman. . . so that we might receive adoption as sons" (Gal 4,4-5).

The events linked to the conception and birth of Jesus are contained in the first chapters of Matthew and Luke, generally called "the infancy Gospel", and it is to them that reference must be made.

Luke's text, used in the prayer of the Angelus is the basis of the Church's teaching on the motherhood and virginity of Mary. The first moment of the mystery of the Incarnation of the Son of God is identified with the miraculous conception which took place by the power of the Holy Spirit when Mary uttered her "yes", "Be it done to me according to your word" (Lk 1,38).

The virginal conception of Jesus on the part of Mary constitutes a particular sign of the divine origin of Mary's Son. Jesus did not have an earthly father because, generated "without human intervention", he assumes human nature his Father remains exclusively God.

The revelation of the intervention of the Holy Spirit in the conception of Jesus, indicates the beginning of the history of the man of the new "spiritual generation" which has a strictly supernatural character (cf. 1 Cor 15,45-49).

In the economy of this self-communication of God to the creature, the virginal conception of Jesus through the power of the Holy Spirit, is a central and culminating event, initiating the new creation.

In this way God enters decisively into history to activate man's supernatural destiny, or the predestination of all things in Christ. It is the definitive expression of God's salvific love for man.

In the conception of Jesus through the power of the Holy Spirit Mary participates in a decisive way. Mary expresses her will and her consent and agrees to become the humble instrument of the "power of the Most High."

The action of the Holy Spirit ensures that in Mary motherhood and virginity are simultaneously present in a way which, although incomprehensible to the human mind, enters fully within the scope of God's predilection and omnipotence.

Isaiah's great prophecy is fulfilled in Mary, "a virgin shall conceive and bear a son" (Is 7,14; cf. Mt 1,22-23) Her virginity, an Old Testament sign of poverty and availability to God's plan, becomes the sphere of the exceptional action of God who chooses Mary to be the Mother of the Messiah.

According to Luke's Gospel, the genealogy of Jesus (Lk 3,23-28) is in ascending order, from Jesus through his ancestors it goes back to Adam.