Justin Martyr

Moreover, the prophecy, "Behold, the virgin shall conceive, and bear a son," was uttered respecting Him. For if He to whom Isaiah referred was not to be begotten of a virgin, of whom did the Holy Spirit declare, "Behold, the Lord Himself shall give us a sign: behold, the virgin shall conceive, and bear a son?" For if He also were to be begotten of sexual intercourse, like all other first-born sons, why did God say that He would give a sign which is not common to all the first-born sons? But that which is truly a sign, and which was to be made trustworthy to mankind,--namely, that the first-begotten of all creation should become incarnate by the Virgin's womb, and be a child,--this he anticipated by the Spirit of prophecy, and predicted it, as I have repeated to you, in various ways.