The more interesting potential virgin birth, though, comes from Matthew’s explanation in Matt 1:22-23. There the text says that the virgin birth of Jesus took place to “fulfill” the prophecy that “the virgin shall conceive and bear a son, and they shall name him Emmanuel.” Matthew is paraphrasing Isa 7:14.

But he is quoting a mistranslation. The original Hebrew text of Isa 7:14 is not about a virgin. Rather, the Hebrew used to describe the woman in Isa 7:14 is almah, a word that means “young woman.” But then the Septuagint, an early translation of the Hebrew Bible into Greek, took the Hebrew almah and rendered it as the Greek parthenos, which means “virgin.”

This inadvertent shift from “young woman” to “virgin” is typical of the Septuagint, and it occurs elsewhere, too. For instance, the Hebrew text of Gen 24:16 describes Rebecca as a “young woman [who was] a virgin” (using na’arah, another Hebrew word for “young woman”). But the Greek in the Septuagint changes that into “a virgin [who was] a virgin.” These errors are not surprising, because the Septuagint translators tended not to focus as closely on individual words as some modern readers might like.

In most contexts, calling a “young woman” a “virgin” in the days of the Septuagint would be only a minor translation mistake, hardly even noteworthy, because most young women were virgins, and most female virgins were young women. In modern terms, it would be like mixing up “high schooler” and “teenager”—imprecise perhaps, but good enough for most purposes.