Alan,
On the notion that the writer of Matthew quoted from the LXX, the Watchtower and a number of other commentators would disagree with it, since they argue -- perhaps correctly -- that Matthew was originally written in Hebrew.
Since most scholars believe that the writers of Matthew and Luke used Mark as a source while writing their gospels, is it really likely that Matthew was written in Hebrew? Just curious, because I never bought into the idea that Matthew was first written in Hebrew.
Also, I never realized that Matthew and Luke are the only ones to mention the Virgin birth. The following is from the “Interpreter's One Volume Commentary”.
The Hebrew original of the verse quoted from Isa 7:14 speaks of almah, i.e. a "young woman" who shall conceive and bear a son. It is the period of conception and birth, not her virginity, that is of importance for Isaiah. The Greek version of the OT in wide use among Jews from the first cent. B.C. on (the LXX) had translated almah by the Greek word parthenos-virgin. Matt. uses this translation, since it suits his purpose of showing that Jesus was divinely conceived in fulfillment of the Hebrew Scriptures. Although Luke has his own version of the extraordinary birth of Jesus, he does not quote or refer to the virgin birth passage from Isa. Neither Mark, or John, nor Paul has any hint of the virgin birth story; it seems to have become important for the church only in the 2nd cent. as a way of combating the charge that Jesus was not truly human. These stories insisted that he was truly born, although they also served to place Jesus at least on par with the pagan saviour-gods for whom a miraculous birth was claimed. Indeed, the idea of Jesus' virgin birth does not figure at all in the rest of Matt.; it is the conviction that Jesus is Emmanuel...God with us that is more significant than the circumstances of his birth. (Interpreter's One Volume Commentary)
Is it possible that Virgin birth concept was also found in the Q document used by Matthew and Luke?
pseudo