To understand the virgin birth it’s necessary to know a little of human history and God’s righteous laws.
Firstly, the holy scriptures declare that God created humankind for a relationship with Him. However, early on in the relationship, man rebelled against God and put his selfish will at the center, instead of the will his creator. The result of the rebellion and broken relationship was devastating,both for humankind and the created universe. For the first time, death and disorder was introduced into God’s beautiful creation. Unless God provided an answer the destiny of humankind and the universe was utter destruction and eternal separation from God.
Thankfully, in his mercy and grace, God did provide an answer, albeit, it was very costly. To deal with mans sin and the death that is caused by separation from his creator, God required the life of an innocent creature. Before Jesus Christ, was a lamb without blemish or defect i.e. it had to be perfect. The blood from the sacrifice of the lamb provided only a partial covering for human sin but it did enable some relationship between God and man. However, a better and lasting sacrifice was to come in the person of Jesus Christ.
When John the Baptist saw Jesus he declared, “Behold, the Lamb of God who takes away the sin of the World.” For this to be true, Jesus had to be perfect i.e. without sin. This was true for two reasons. Firstly, he was born without a ‘sin nature’. Starting with Adam, the sin nature is passed down the male line i.e. we inherit it at birth. Notice, you don’t have to teach a child to be selfish or to do wrong! Through the divine conception and the virgin birth, Jesus was fully man and fully God. Perfect from birth and never committing a sin in his life (he only ever did the will of his heavenly father!), he was the Lamb of God, able to fully satisfy the righteous requirements of punishment for sin by a just God!