"O Lord, wishing to fulfill all things..."

Icon of Holy Theophany: the Baptism of Christ and the Revelation of the Holy Trinity (source)

  
O Lord, wishing to fulfill all things that You ordained before the ages, You received the servants of Your mystery, from among the Angels, Gabriel, from among Men, the Virgin, from among the Heavens, the Star, and from among the Waters, the Jordan, in which You washed away the sin of the world, O our Savior, glory to You.
-Doxastikon of the Liti for the Great Feast of Theophany,
St. John of Damascus

(source)
  

Through the prayers of our Holy Fathers, Lord Jesus Christ our God, have mercy on us and save us! Amen!