Tanakh — Prophecy
Isaiah 7:14
"Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel."
The Hebrew word "alma" can mean "young woman" or "virgin." Jewish tradition interprets this as a sign for Isaiah's time, while Christians see a dual fulfillment in the virgin birth of Jesus.
New Testament — Fulfillment
Matthew 1:22-23
"Mary, a virgin, gives birth to Jesus, fulfilling this prophecy as Immanuel, meaning "God with us.""