The answer is: Isaiah

Matthew 1:23 / Isaiah 7:14 - part of a difficult passage of prophecy written some 700 years before the birth of Jesus.

It's remarkable to think about the continuity in the biblical text—Isaiah's prophecy paints a vivid portrait over seven centuries before the birth of Jesus. When Isaiah declared that a virgin would conceive, he delivered a message rich in hope during a time of political upheaval for Israel. The word "virgin" stirred quite a debate among scholars and translators for centuries, leading to considerations of original Hebrew interpretations.

One interesting trivia tidbit: the Hebrew term "almah" used in Isaiah can refer to a young woman of marriageable age, and traditionally religious understanding connected it to a miraculous event. This adds a fascinating layer of speculation about not only the prophetic significance but also how language evolves and deepens over time.

Moreover, this prophecy's echo stretches beyond Christianity into Jewish thought as well, in discussions about the Messiah. Interpretation can vary widely; for instance, many within Judaism view this prophecy not as pertaining to a future messianic figure but as historical accounts relevant to Isaiah's present context.

There’s something beautifully poetic about these prophetic narratives; they stir the imagination and provoke thought into life’s mysteries and promises. Imagine the centuries of anticipation leading up to the Nativity story—an instance where theology, culture, and human experience intertwine to showcase light breaking through darkness, a theme that resonates universally.