βTherefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son, and shall call his name Immanuelβ (Isaiah 7:14).
While Christendom speaks of the βvirgin birth of Christ,β according to todayβs Scripture, a more accurate term would be the βvirgin conception of Christ.β There was nothing unusual about Christβs birth; it was His conception that was unique because there was no human father!
Interestingly, todayβs Scripture has been the point of controversy for over a century (to Satanβs delight!). Some modern Bibles (RSV, NRSV, et al.) translate the Hebrew word here translated βvirginβ as the vague βyoung woman,β thereby leaving room for the heretical idea that Joseph was Jesusβ biological father (and denying Christβs deity)! If someone ever tells you almah (the Hebrew word translated βvirginβ) can mean βyoung womanβ or βvirgin,β they are right, but point out that the key to choosing the right translation is not up to a translator, but rather the Holy Ghost!
The author of Matthewβs Gospel, filled with the Holy Ghost, knew which translationββyoung womanβ or βvirginββwas what God had intended in Isaiah 7:14. If we want to know what God meant in Isaiah 7:14, why not ask God?
βNow all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying, βBehold a virgin shall be with childβ¦β (Matthew 1:22,23a). The Greek word translated βvirgin,β parthenos, can only mean βvirgin,β not βyoung woman.β Isaiah was prophesying a virgin, indicated by the words βfirstborn sonβ (Matthew 1:25; Luke 2:7) and βJoseph knew her not till she had brought forth her firstborn sonβ (Matthew 1:25). Isaiah 7:14 meant βvirgin,β as indicated by Luke 1:34, for Mary βknew not a man.β Again, the Bible is clear that Joseph was not Jesusβ biological father.
Matthew 1:23 indisputably proves that almah in Isaiah 7:14 did not simply mean a βyoung woman,β who may or may not be sexually pure, but βa virgin,β a woman who never had any sexual intercourse. The Holy Ghost, not Joseph, was the Father of Jesusβ body (Matthew 1:18-20). source