In the church calendar from December 17th to the morning Mass for Christmas Eve, each day has its own special prayers. So today we are celebrating Advent for the 21st of December, and the O Antiphon that is proper for today is O Radiant Dawn. Let us pray. Hear in kindness, O Lord, the prayers of Your people, that those who rejoice at the coming of Your only begotten Son in our flesh, may when at last He comes in glory, gain the reward of eternal life, through our Lord Jesus Christ, Your Son, who lives and reigns with You in the unity of the Holy Spirit, one God forever and ever, Amen.