Let's Talk About Christmas

The New Testament teaches that Christians are to "contend earnestly" (NKJV) or "fight hard" (NJB) for the faith given once for all of God's saintly people (Jude 3). Was Christmas part of the original faith? Did early Christians observe Jesus' birthday? Did the custom of gift giving come from the 'three wise men' or from pagan observances? Did Tertullian of Alexandria warn that Greco-Romans who professed Christianity were compromising with the heathen by participating in idolatrous observances such as Saturn