Isaiah 7:14 Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel.
Why is it so important that a virgin be the one to become pregnant with Jesus? Since the beginning, when Adam and Eve sinned and introduced a corrupt nature into all of mankind, we’ve been tainted. We can’t be good no matter how hard we try because we have that sinful nature.
Some have tried to convince us that a virgin birth was necessary in order for Jesus to be without a sinful nature. The logic is that the sinful nature must be passed down from generation to generation from the father. This may be the case, but a mother is also a sinful human being and therefore capable of passing down her sinful nature to her offspring.
Mary was a real person with a real human body and within that body was the Christ child. No other person ever had such a physical connection with Jesus than did His birth mother. How she became pregnant with the Son of God is where the importance of her virginity becomes important. Mary conceived without the help of a man. She was impregnated supernaturally by the Holy Spirit. Because He did this work in her to bring about the Christ’s birth into the world, there was no earthly explanation for her pregnancy. The supernatural circumstances of her pregnancy make it the only time in the history of humankind for a baby to be born with no earthly father involved. This was the sign promised in Isaiah, hundreds of years before.