"Therefore the Lord Himself will give you a sign: Behold a virgin shall conceive and bear a Son, and shall call His name Immanuel." (Isaiah 7 :14)
"Then the angel said to her, "Do not be afraid, Mary, for you have found favor with God. And behold, you will conceive in your womb and bring forth a Son, and shall call His name Jesus. He will be great, and will be called the Son of the Highest: and the Lord God will give Him the throne of His father David." (Luke 1:30-32)
The Prophecy fullfilled
"Then the angel said to them, Do not be afraid, for behold, I bring you good tidings of great joy which shall be to all people. For there is born to you this day in the city of David a Savior, who is Christ the Lord. And this will be the sign to you: You shall find the Babe wrapped in swaddling cloths, lying in a manger." (Luke 2:11-13)
This is the true joy of Christmas, our Saviors' birth.
Merry Christmas.