Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.
All Commentaries on Matthew 1:23 Go To Matthew 1
Theophylact of Ochrid
The Jews say that it is not written in the prophecy "virgin" but "young woman." To which it may be answered that "young woman" and "virgin" mean the same thing in Scripture, for in Scripture "young woman" refers to one who is still a virgin. Furthermore, if it was not a virgin that gave birth, how would it be a sign, something extraordinary? Listen to Isaiah who says, "For this reason the Lord Himself shall give you a sign," and immediately he adds, "Behold, the Virgin" (Is. 7:14). So if it were not a virgin that would give birth, it would not be a sign. The Jews, then, alter the text of Scripture in their malice, putting "young woman" instead of "virgin." But whether the text reads "young woman" or "virgin," it should be understood in either case that it is a virgin who will give birth so that the event may be a miraculous sign.
The Jews say, "How then is it that He was not called Emmanuel but Jesus Christ?" One may answer, "The prophet did not say ‘You shall call,’ but ‘They shall call.’" That is, the events and deeds of His life will show that He is God and that He keeps company with us. For Holy Scripture gives names that are derived from the events of one’s life; for example, "Call his name Plunder Swiftly" (Is. 8:3). Yet where does it record that anyone was ever called by such a name? But since error was despoiled and taken captive at the moment of the Lord’s birth, Scripture gives this as His name, which He acquires from the event.