Everyone knows the story. The angel Gabriel appears to Mary. He tells her that she will have a child who will save his people and establish his kingdom. But there is a problem. As Mary asks, “How will this be, since I am a virgin?” (Luke 1:34).
The angel Gabriel explains, “The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the child to be born will be called holy—the Son of God” (Luke 1:35). Instead of doubt, Mary believes. She confesses: “Behold, I am the servant of the Lord; let it be to me according to your word” (Luke 1:38). She believed and did not waver.
Why did God decide that Jesus would be born in this particular way? Why did God use a virgin birth to bring Jesus into the world? There are at least three answers.
To fulfill prophecy
First, the prophet Isaiah prophesied that the coming one would be born of a virgin. Isaiah 7:14 says, “Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel.” In particular, this prophecy of Isaiah shows that the virgin birth functions as “a sign” of God.
What sort of sign? In the context of Isaiah 7, it signifies God’s promise of salvation to Judah because Ephraim and Syria have allied against Judah. Yet something unexpected happened.
God did not provide one child as a sign but many: “Behold, I and the children whom the Lord has given me are signs and portents in Israel from the Lord of hosts, who dwells on Mount Zion” (Isa 8:17; cf. 7:3). Isaiah takes the prophecy of Isaiah 7:14 as a sort repetitive sign of God’s promise. Each child portends God’s salvation.
And yet God did say the child’s name shall be “Immanuel” (Isa 7:14). And even though Isaiah has signs of God’s promise, God continues to promise a child (Isa 9:1–7). In one of the most beautiful passages in Scripture, the Lord says through Isaiah: ”For to us a child is born, to us a son is given; and the government shall be upon his shoulder, and his name shall be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace” (Isa 9:6).
Now the description of the child here (e.g., “Mighty God”) goes beyond any description that would be appropriate for the children of Isaiah. In fact, this child will have an unending kingdom (Isa 9:7). So while Isaiah does see the birth of his children as “signs and portents,” these earlier signs only whet our appetite for the coming child—the Prince of Peace.
Hence, the virgin birth fulfills the prophecy of Isaiah in order to establish the uniqueness and particular duties of this coming child. He will bring peace and establish an unending kingdom. It is not only a prophecy about the future. Rather, it is a prophecy that cements the identity of Immanuel.
To establish his divine origin
The name “Immanuel” (Isa 7:14) means “God with us.” In this light, the prophecy of Isaiah 7:14 provides vital insight into the identity of the child. He will signify God’s real presence among his people. There are many ways that we could conceive of this happening.
Yet Isaiah 9 and 11 provide further insight into the identity of the virgin-born child. This child will do something quite remarkable. He will bring peace, end the exile, and establish an unending Davidic kingdom. As Isaiah 11:10 records, “In that day the root of Jesse, who shall stand as a signal for the peoples—of him shall the nations inquire, and his resting place shall be glorious.”
Therefore, the virgin-born Immanuel will do something that requires the miraculous power of God. And this power finds a root in the Holy Spirit: “And the Spirit of the Lord shall rest upon him, the Spirit of wisdom and understanding, the Spirit of counsel and might, the Spirit of knowledge and the fear of the Lord” (Isa 11:2).
The Spirit of the Lord (i.e., Yahweh) will empower Immanuel to accomplish his task. In this sense, it becomes clearer how God could be among his people. Perhaps it is through the Holy Spirit? The Gospel books confirm this, yet they say much more.
In Luke’s account, Gabriel tells Mary, “The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the child to be born will be called holy—the Son of God” (Luke 1:35). The Spirit’s work of generation in Mary’s womb does not, however, sum up the whole event.
An angel tells the shepherds that the baby is “Christ the Lord” (Luke 2:11). The word “Lord” should tip us off since it echoes the Old Testament’s primary title for God, “LORD.” What Luke intimates through the whole story of Jesus’s life, death, and especially his resurrection, John says quite plainly: “The Word was God” (John 1:1).
The virgin birth establishes Jesus’ divine origin through the Holy Spirit’s act in Mary’s womb. In some mysterious and glorious way, the Spirit unites humanity to the divine Word of God. Jesus is and always was the union of God and man: Immanuel, God with us.
To confirm his sinless humanity
Given Jesus’ divine origin that the virgin birth underscores, we can now understand why Jesus could be like us in every way “yet without sin” (Heb 4:15). While the human flesh may be weak, the power of the incorruptible God is not. Christ as one person with two natures could withstand relentless temptation (without ever caving to temptation to relieve the suffering of temptation) because of his divine nature.
We must also affirm, although I cannot claim to be able to explain it, that Christ did not have a fallen nature. Whether that is because original sin comes by way of human fathers or because the Holy Spirit formed the child or because of some other reason, I do not know.
Of course, a lot more could be said about why God came to visit us. He came to redeem us from our sins, to overcome death, and to defeat the devil. Yet the question here concerns why God chose the virgin birth of Jesus. In answer, he did so to fulfill prophecy, to establish Jesus’ divine origin, and to confirm Christ’s sinless humanity.
And this truth leads us to make the amazing claim God visited us in our frailty and weakness in order to save us from our sins. Had God not become what we are, then we would remain what we were—dead in sin, children of wrath.
Instead, we have become by adoption (children of God) what Christ is by nature (the Son of God). By following his Spiritual birth, we too are all born of the Spirit. And we follow the firstborn of the new creation into heaven where we will have joy forevermore.
Joy to the world, indeed, for the Lord has come!