Because God is sovereign over the future, he alone is capable of giving prophetic insight into the future. In great mercy he did this for his people in the Old Testament. He detailed for them who was coming to save them, how he would come, where he would come, when he would come, and why he would come, so that they would anticipate the incarnation and salvation of Jesus Christ.
Around 4000 bc, after Adam and Eve sinned, God prophesied to them that the Messiah would be born of a woman; he makes no reference to a father, which intimates the virgin birth. This prophecy was given by God himself and was the first time the gospel was preached: “I will put enmity between you [the Serpent] and the woman, and between your offspring and her offspring; he shall bruise your head, and you shall bruise his heel.”
Around 700 bc Isaiah prophesied exactly how Jesus would come into human history: “Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel.” The promise that Jesus’ mother would be a virgin who conceived by a miracle did, in fact, come true. Jesus’ mother, Mary, was in fact a godly young woman and chaste virgin who conceived by the miraculous power of God the Holy Spirit. Jesus, a name that means “he saves his people from their sins,” came as “Immanuel,” which means, “God is with us.” God became a man at the incarnation of Jesus.
Matthew 1:22-23 reveals that Isaiah’s prophecy came true: “All this took place to fulfill what the Lord had spoken by the prophet: ‘Behold, the virgin shall conceive and bear a son, and they shall call his name Immanuel.’
In roughly 700 bc Micah prophesied that Jesus would be born in the town of Bethlehem, saying, “But you, O Bethlehem Ephrathah, who are too little to be among the clans of Judah, from you shall come forth for me one who is to be ruler in Israel, whose coming forth is from of old, from ancient days.”
This prophecy was fulfilled in Luke 2:1-7. Caesar Augustus had called for a census to be taken, which required that every family register in their hometown. Jesus’ adoptive father, Joseph, was thus required to return to Bethlehem because he was a descendant of the family line of David. In God’s providence, this census was required right when Mary was pregnant; she journeyed with her husband from their home in Nazareth to Bethlehem so that Jesus was born in Bethlehem in fulfillment of Micah’s prophecy.
As to the timing of Jesus’ incarnation, in 400 bc Malachi prophesied, “Behold, I send my messenger, and he will prepare the way before me. And the Lord whom you seek will suddenly come to his temple; and the messenger of the covenant in whom you delight, behold, he is coming, says the Lord of hosts.” The messenger of whom Malachi spoke was John the Baptizer, who prepared the way for Jesus’ incarnation to bring the new covenant, and the Lord he speaks of is the Lord Jesus Christ. It is important that we are told that Jesus would come to “his temple.” Since the temple was destroyed in ad 70 and has not existed since, this places the incarnation of Jesus Christ prior to ad 70. Practically, this means that our Jewish friends who are still awaiting the coming of their Messiah missed him; they wait in vain because he has already come to his temple and brought the new covenant of salvation.
Isaiah prophesies in 700 bc about why Jesus would become incarnate—he is God’s arm of salvation reaching down to save sinners.34 Isaiah also says that Jesus would come from humble circumstances and suffer great sorrow and grief by men in order to deal with the human sin problem through his death, burial in a rich man’s tomb, and resurrection.
The purpose of Jesus’ incarnation was fulfilled when, just as promised, he suffered and died in the place of sinners though he himself was sinless, was buried in a rich man’s tomb, and rose from death to make righteous the unrighteous.