Isaiah 7:14 Therefore the Lord Himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call His name Immanuel.
The Athanasian Creed (LSB, pp. 319-20) speaks of the incarnation: “He is God, begotten from the substance of the Father before all ages; and he is man, born from the substance of His mother in this age. … Although He is God and man, He is not two, but one Christ … not by the conversion of the divine into flesh, but by the assumption of the humanity into God” (vv. 29, 32, 33).
From Luther’s Small Catechism with Explanation – 2017 Edition
(Mary and Jesus via wikipedia. PD-US)