In the early centuries of the Church, the days after Christmas became associated with various important figures and events. By at least the sixth century in France and Italy, December 27 commemorated St. John the Apostle and Evangelist, and the collect for today has been handed down with only slight changes since that time. It reads:
Merciful Lord, we beseech thee to cast thy bright beams of light upon thy Church, that it, being illumined by the doctrine of thy blessed Apostle and Evangelist Saint John, may so walk in the light of thy truth, that it may at length attain to life everlasting; through Jesus Christ our Lord. Amen.
Commemorating John near Christmas is appropriate because his Gospel proclaims the mystery of the Incarnation, the Word becoming flesh and dwelling among us. Jesus Christ is the light that shines in a dark world and is not overcome by the darkness!