Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel.
Isaiah 7:14, ~ 700 BC.
The Reformation Study Bible notes,
"virgin" - The Hebrew word occurs seven times in the Old Testament. It means a young woman of marriageable age, normally a virgin (Gen. 24:43). The Septuagint (the Greek translation of the Old Testament made about 150 b.c.) translated with a word more specifically meaning “virgin.” The New Testament understands Isaiah to be designating the Virgin Mary (Matt. 1:23). See “The Virgin Birth of Jesus” at Luke 1:27.
"Immanuel" - “God with us.” The name conveys God’s promise to save, bless, and protect His children.
Read more in the Reformation Study Bible.