In Luke’s Gospel, as we have seen, the angel Gabriel announces to Mary that she will have a child:
Luke 1:34 And Mary says to the angel, “How can this be, since I am a virgin?”[13] 1:35 The angel responds, “The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the child to be born will be holy; he will be called Son of God.”[14]Matthew’s Gospel includes the reason why Mary’s virginity is essential to the story:
Matt 1:18 Now the birth of Jesus the Messiah took place in this way. When his mother Mary had been engaged to Joseph, but before they lived together, she was found to be with child from the Holy Spirit. 1:19 Her husband Joseph, being a righteous man and unwilling to expose her to public disgrace, planned to dismiss her quietly.[15] 1:20 But just when he had resolved to do this, an angel of the Lord appeared to him in a dream and said, “Joseph, son of David, do not be afraid to take Mary as your wife, for the child conceived in her is from the Holy Spirit. 1:21 She will bear a son, and you are to name him Jesus, for he will save his people from their sins.” 1:22 All this took place to fulfill what had been spoken by the Lord through the prophet: 1:23 “Look, the virgin shall conceive and bear a son, and they shall name him Emmanuel,” which means, “God is with us.” 1:24 When Joseph awoke from sleep, he did as the angel of the Lord commanded him; he took her as his wife, 1:25 but had no marital relations with her until she had borne a son; and he named him Jesus.[16]
To understand how Matthew finds a virginal conception in the Prophets, we need to compare the Hebrew and Greek (Septuagint) versions of Isaiah 7:14. In the Hebrew, Isaiah states,
ישעיה ז:יד לָכֵן יִתֵּן אֲדֹנָי הוּא לָכֶם אוֹת הִנֵּה הָעַלְמָה הָרָה וְיֹלֶדֶת בֵּן וְקָרָאת שְׁמוֹ עִמָּנוּ אֵל.
Isa 7:14 Therefore, the Lord himself will give you a sign. Look, the young woman (ʿalmah) is pregnant and shall bear a son, and she will call his name Emanu-El.”
When Isaiah was translated into Greek,[17] centuries before Matthew, ʿalmah was rendered as parthenos (παρθένος), which, at the time, meant both “young girl”—the Greek of Genesis 34 describes Dinah as a parthenos after she and Shechem had sexual relations—as well as “virgin,” as in the Parthenon, the temple to the virgin Athena. By Matthew’s time, parthenos was generally taken to mean “virgin.” Matthew, reading Isaiah in Greek, finds a virginal conception; other Jews, reading the Hebrew, do not.
"The Jewish Origins of the Christmas Story", Amy-Jill Levine (here)
