One person esteems one day above another; another esteems every day alike. Let each be fully convinced in his own mind. He who observes the day, observes it to the Lord; and he who does not … to the Lord he does not observe it … why do you judge … Or why do you show contempt for your brother? For we shall all stand before the judgment seat of Christ. Romans 14:5–6, 10 NKJV
God had told His earthly people Israel to observe special feast days, telling them how, when, and with what sacrifices they were to be celebrated. While some Jewish Christians continued celebrating these feasts, and still do to this day, God no longer commands them to do so. The Holy Spirit also made very clear at the meetings at Jerusalem in Acts 15 that circumcision and the Law were absolutely not to be imposed on Gentile believers.
Gentiles of many nations, each with its own god or gods, also had held feasts to their many idols. God’s Word tells us, “The things which the Gentiles sacrifice they sacrifice to demons and not to God, and I do not want you to have fellowship with demons” (1 Cor. 10:20). Idolatrous Gentile feasts clearly were not equivalent to the feasts that God had commanded His earthly people Israel to celebrate to Him. The only feast the Lord has requested His own to celebrate to Him is the breaking of bread.
The early Christians observed the Lord’s death and resurrection, not His birth, the date of which was unknown. Christianity was legalized in the Roman Empire in 313 ad. Celebrating Christ’s birth on December 25 was made official by Pope Julius I around 350 ad. It replaced the heathen festival of Saturnalia formerly kept around that time. However, we must not judge our brethren who act according to their convictions before the Lord, even when our convictions are different. Let us pursue things that make for peace and edify!