Irmos of the ninth ode of the Canon at Matins for the Theophany of our Lord God and Saviour Jesus Christ (Jan 6/19). Tone 2.
It is also sung at the Divine Liturgy on that day and during the post-festive period.
Music from the Anthology pp. 793-795
lyrics
O my soul, magnify Christ the King, baptized in the Jordan.
Every tongue is at a loss to praise you as is your due, O Mother of God. Even a spirit from above is filled with dizziness when seeking to sing your praises. But since you are good accept our faith, for you know well our love inspired by God. For it is you who protect all Christians; therefore, we magnify you.