Tradition
St. Cyril of Jerusalem
Catechetical Lectures
Book 12 › Introduction
On the words Incarnate, and Made Man.
Isaiah 7:10-14
“And the Lord spoke again unto Ahaz, saying, Ask you a sign, etc.:” and “Behold! A virgin shall conceive, and bear a son, and shall call His name Emmanuel, etc.”
Source: Catechetical Lectures (New Advent)