The bible does not mention any sort of
celebration for Christ's
birth.
Jesus, the apostles and the early church did
not celebrate His
birth either.
After the 3rd century, Christians started
taking part in blatant
pagan sun worship celebrations.
The Church leaders tried as hard as they
could, but they could
not stop the influence and the spread
of these pagan
celebrations within Christianity
Getting tired of constantly fighting against
them, they decided to
"Christianize" these pagan celebrations and allow them to continue as “Christian”
celebrations
In the 4th century, the Church at Rome
declared December
25th (a well established pagan holiday) as the official birthday of Christ.