The Sticheron "Isaïou Nyn Tou Prophitou" commemorates the birth of John the Baptist (also known as the Forerunner) in the Vespers service of June 24th. The hymn praises the many virtues ot'lohn 's life and brings in references from the Old and New Testaments by stating that the prophecy of Isaiah the prophet was filfilled by the new prophet, John, who prepares the way for the Lord. The musical setting makes frequent uses of tetrachords and their inversions of the intervals of the fifth. Perhaps Kassia's effort in making use of two motives, intervals of fourths and fifths, that are essentially inversions of the same, is a vehicle of musical expression for displaying similarities between the two prophets in the text.
Translation: New the voice of Isaiah the prophet this day has been fulfilled by the conception of one greater than the prophet, John. For behold, He said, I will send my messenger before Your countenance, who shall prepare Your way. He then, as soldier and forerunner of the Heavenly King, truly made straight the paths of our God, being a man by nature, but an angel in his life. For he had embraced complete chastity and self-restraint, he held to that which was according to nature, but avoided that which was contrary to nature, striving beyond nature. Let us all, the faithful, imitate him in virtue, implore him to plead on our behalf for the saving of our souls.