Was the Virgin Birth Necessary? In order to understand whether the virgin birth was necessary, it is important to understand that a perfect angel or a perfect man could not have atoned for sin. Only God Himself can bear the wrath of God, the punishment for man's sin, and rise again! Thus, it is clear that it had to be God who saved His people from their sin. But, on the other hand, it was man who was responsible for his sin. The book of Hebrews provides an explanation as to why Christ had to become man in order to pay for sin:
For assuredly He does not give help to angels, but He gives help to the descendant of Abraham. Therefore, He had to be made like His brethren in all things, so that He might become a merciful and faithful high priest in things pertaining to God, to make propitiation for the sins of the people. (Hebrews 2:16-17)This passage demonstrates that Christ had to become man to pay for man's sins. If He had chosen to to pay for the sins of angels, it seems that He would have had to become angel (this He has not done, for unlike fallen men, whom Christ graciously chooses to save, He did not choose to save the angels that fell). Thus, in order to pay for sin, Christ had to be both God and man— fully God and yet fully man. However, this still does not provide an explanation as to why Christ had to be born of a virgin. Why couldn't He have simply flown down out of heaven in a human body?
The book of Galatians provides an answer to this question (emphasis added):
But when the fullness of the time came, God sent forth His Son, born of a woman, born under the Law, so that He might redeem those who were under the Law, that we might receive the adoption as sons. (Galatians 4:4-5)It seems that if Christ had not been born under the law, He would have been unable to redeem those who were under the law. In Christ being born of the virgin Mary, it also made plain that Christ was indeed man. If Christ had not been born of a woman, would it really be appropriate to consider Him part of Eve's seed? (see Genesis 3:15)
It should also here be pointed out that in whatever way Jesus was conceived of by the Holy Spirit, He avoided the stain of original sin. There are differing opinions as to how original sin is passed on (federal headship, seminal headship, etc.), but regardless of which view a person may hold, Christ was miraculously kept from being born as the rest of humanity: by nature children of wrath (see Ephesians 2:3).
Why was the Virgin Birth So Important? The virgin birth marked the fulfillment of many prophecies: The Messiah had to be a descendant of David (see Psalm 89:3-4). Isaiah even specifically prophesied that the Messiah would be born of a virgin (see Isaiah 7:14). To list all of the Old Testament prophecies concerning the coming of the Messiah would be a lengthy task. But perhaps the most amazing promise of the coming Messiah can be found in the beginning of Genesis. Shortly after creation, when man sinned and fell, God promised that man would bruise Satan on the head (see Genesis 3:15). The Messiah is the fulfillment of this promise— for Jesus Christ is the only man to ever strike Satan with a fatal blow.
The virgin birth is also of great importance because it marked Jesus' entrance into the world. It marked the beginning. The beginning of redemption. Without the virgin birth, man would be without hope. All men would be found guilty and condemned to hell for eternity. But because of the virgin birth, because Christ became flesh and entered this world, salvation is possible! Despite man's indescribable wickedness, the door of salvation is open! And all who look to the cross, all who put their trust in Christ— that He alone can redeem, will be saved. That is the ultimate reason for the virgin birth— that God be glorified in saving His people from their sin.
The Westminster Confession (Chapter VIII, Section II) beautifully states some of these important truths which have just been discussed:
The Son of God, the second Person in the Trinity, being very and eternal God, of one substance, and equal with the Father, did, when the fullness of time was come, take upon him man's nature, with all the essential properties and common infirmities thereof; yet without sin: being conceived by he power of the Holy Ghost, in the womb of the Virgin Mary, of her substance. So that two whole, perfect, and distinct natures, the Godhead and the manhood, were inseparably joined together in one person, without conversion, composition, or confusion. Which person is very God and very man, yet one Christ, the only Mediator between God and man.
Christianity, Isalm, and the Virgin Birth - The Christian Worldview
Was the Virgin Birth Necessary? Why was the Virgin Birth So Important? (Part 1)
The Virgin Birth - Matthew 1:18
Isaiah's Prophecy: It's Fulfillment (Part 1) - Matthew 1:22-23
Jesus' Purpose: To Save His People From Their Sins (Part 1) - Matthew 1:21