John taught that God became a man: “the Word was God... And the Word became flesh” (John 1:1, 14). When did the Word become flesh?
“Christ Jesus, who, although He existed in the form of God, did not regard equality with God a thing to be grasped, but emptied Himself, taking the form of a bond-servant, and being made in the likeness of men” (Philippians 2:5-7).
When was Christ Jesus made in the likeness of men? The angel Gabriel told a young woman named Mary,
"behold, you will conceive in your womb and bear a son, and you shall name Him Jesus. He will be great and will be called the Son of the Most High; and the Lord God will give Him the throne of His father David" (Luke 1:31-34).
Mary asked Gabriel how such a thing could happen, since she was a virgin, and he said, "The Holy Spirit will come upon you, and the power of the Most High will overshadow you; and for that reason the holy Child shall be called the Son of God” (Luke 1:35). God became a man in the person of Jesus Christ, the son of a virgin named Mary, conceived by the power of the Holy Spirit, a plan God (the Father, the Son, and the Holy Spirit, Matthew 28:19, 1 Peter 1:2, Ephesians 1:17) had from the creation of the world. As Peter wrote, “Christ, a lamb without blemish or defect... was chosen before the creation of the world, but was revealed in these last times for your sake” (1 Peter 1:19-21). In the Garden of Eden when death entered the world through sin, the virgin birth is foretold when God cursed the Serpent saying, “I will put enmity between you and the woman, and between your seed and her seed; he shall bruise you on the head, and you shall bruise him on the heel" (Genesis 3:15). The male seed of woman defeating the Serpent was always God’s plan for overcoming sin and death. Later, when God commanded Abraham to sacrifice his one and only son Isaac at Moriah (the temple mount where Jerusalem stood, Genesis 22:2, 2 Chronicles 3:1), Isaac asked where the lamb was for the offering. Abraham prophesied that the Lord would provide the lamb (Genesis 22:8, 1 Peter 1:19-21), which he did then with a ram, but ultimately by bringing His son into the world, through the incarnation and virgin birth (Hebrews 1:5-6).
God had explicitly told the prophet Isaiah in about 730 B.C. that he would provide a sign in the form of a virgin conceiving and bearing a son who would be called “God with us” (Immanuel, Isaiah 7:14, Matthew 1:22-23). The character of this human male and his kingdom, born of a virgin with a divine nature, is described in Isaiah 9:6-7 where he is referred to as “Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace.” A fundamental reason for the coming of this son, the seed of woman, is described in Isaiah 59:6-17 and Isaiah 63:3-6 where the Lord describes humanity’s devastating sin problem, that all have sinned and none are righteous, resulting in God’s wrath and just punishment of sinners. However, God wanted not just justice, but justification, not wrath but redemption. In Isaiah 59:16 and again in Isaiah 63:5 God is described as being appalled that there was no human answer to the human problem of sin and death and wrath, “He saw that there was no one, he was appalled that there was no one to intervene; so his own arm worked salvation for him.” God would do for man what man could not do for himself. Paul restates these problems in the book of Romans, describing the universal problem of sin and death in Romans 1-3 (quoting from Isaiah 59:7-8 in Romans 3:15-17) and assuring us that there is an answer because God entered into human history as promised, “his own arm worked salvation for him,” in Romans 3:21-26. Jesus, born of a virgin, did what no other man was able to do, because he is also God’s right arm, the one and only Son of God, who could deal with temptation as a man, give himself as the unblemished lamb of God, and rise from the dead in verification of his divine nature. He was the human son of David in the flesh (through Mary), and was God in the flesh (Romans 1:1-5). The human and divine nature of Jesus Christ is celebrated in Hebrews 2:5-18 as the unique and all sufficient answer to the problem of sin and death, and reigning Lord.
In the last days of king David’s dynasty in Jerusalem, the prophet Jeremiah said that the current heir of David, Jehoiachin, would never have a son sitting on David’s throne (Jeremiah 22:30). This was a conundrum, since the son of David was to occupy his throne forever! Matthew gives us the lineage of Jesus’ legal father Joseph in Matthew 1, including Joseph’s descent from Jehoiachin (also called Jeconiah) in Matthew 1:11-12. According to Matthew Joseph is an heir of David, through Jehoiachin, but according to Jeremiah no seed of Jehoiachin (and thus of Joseph) could occupy David’s throne. Then we see that Joseph was the legal but not physical father of Jesus, who was conceived by the Holy Spirit in the womb of Joseph’s fiancée Mary. The prophets required a son of David, a legal heir to the throne, and at the same time no descendant of Jehoiachin, the last of David’s dynasty in Jerusalem. The virgin birth was God’s plan to meet that need.
Paul in Romans 5:6-21 described how sin entered the world through a man, and so a man had to deal with it. However, as God observed in Isaiah 63:5, there was no such man to be found, and so he had to do it himself, as a man. Similarly in 1 Corinthians 15:45-49 Paul wrote that Adam is the first man, and Jesus the last Adam, the 2nd man, and that we need both the physical from the first, and the spiritual from the 2nd , “the man from heaven”.
When God became a man in the womb of a young virgin named Mary he showed his commitment to fulfill all his promises, not depending on some man, any man, but entering into human history himself to do what no other man would or could do, in full obedience and at any cost. Truly, as John wrote, “This is how God showed his love among us: He sent his one and only Son into the world that we might live through him” (1 John 4:9).
(Scripture quotes from NASU and NIV)