On this day, in addition to the Fourth Sunday of Advent, the Church commemorates St. Thomas. The Treasury of Daily Prayer notes:
All four Gospels mention St. Thomas as one of the twelve disciples of Jesus. John's Gospel, which names him "the Twin," uses Thomas' questions to reveal truths about Jesus. It is Thomas who says, "Lord, we do not know where you are going, so how can we know the way?" To this question Jesus replies, "I am the way, and the truth, and the life" (John 14:5-6). John's Gospel also tells how Thomas, on the evening of the day of Jesus' resurrection, doubts the report of the disciples that they had seen Jesus. Later, "doubting Thomas" becomes "believing Thomas" when he confesses Jesus as "my Lord and my God" (John 20:24-29). According to tradition, Thomas travelled eastward after Pentecost, eventually reaching India, where still today a group of people call themselves "Christians of St. Thomas." Thomas was martyred for the faith by being speared to death.
Prayer: Almighty and ever-living God, You strengthened Your apostle Thomas with firm and certain faith in the resurrection of Your Son. Grant us such faith in Jesus Christ, our Lord and our God, that we may never be found wanting in Your sight; through the same Jesus Christ, who lives and reigns with You and the Holy Spirit, one God, now and forever. Amen.
In today's Prayer of the Church, our Synod prayed: "O Lord God, through the life, death, and resurrection of Your Son, Jesus Christ, and by the power of the Holy Spirit, the revelation of Your salvation mystery is now revealed and made known to all the nations. Grant that this mystery of salvation, as confessed by St. Thomas and all those who now rest from their labors, may continue to guide Your Church on earth as we wait for the day when You come from heaven one last time and usher in the new creation."