Now the birth of Jesus Christ was on this wise: When as his mother Mary was espoused to Joseph, before they came together, she was found with child of the Holy Ghost. Matthew 1:18 KJV
The conception of Mary, the mother of Jesus was a supernatural act of the Holy Ghost (Holy Spirit). It brought about the birth of the Only Begotten Son of God.
Jesus was born a human without a sin nature because His Father was the Holy God Almighty. He was very God and very man. God sent His Son to redeem whosoever will receive Him.
For God sent not his Son into the world to condemn the world; but that the world through him might be saved. John 3:17 KJV
To Celebrate Christmas is to Celebrate the birth of the Messiah of Israel and Savior of the world.
And, lo, the angel of the Lord came upon them, and the glory of the Lord shone round about them: and they were sore afraid. And the angel said unto them, Fear not: for, behold, I bring you good tidings of great joy, which shall be to all people. For unto you is born this day in the city of David a Saviour, which is Christ the Lord. And this shall be a sign unto you; Ye shall find the babe wrapped in swaddling clothes, lying in a manger. And suddenly there was with the angel a multitude of the heavenly host praising God, and saying, Glory to God in the highest, and on earth peace, good will toward men. Luke 2:9-14 KJV