Ancient Syriac Documents. Moses of Chorene. History of Armenia.
IV. Abgar returns from the east; he gives help to Aretas in a war against Herod the Tetrarch.
When Abgar had returned from the East, he learnt that the Romans suspected him of having gone there to raise troops. He therefore made the Roman commissioners acquainted with the reasons of his journey to Persia, as well as the treaty concluded between Ardachès and his brothers; but no credence was given to his statement: for he was accused by his enemies Pilate, Herod the tetrarch, Lysanias and Philip. Abgar having returned to his city Edessa leagued himself with Aretas, king of Petra, and gave him some auxiliary troops under the command of Khosran Ardzrouni, to make war upon Herod. Herod had in the first instance married the daughter of Aretas, then had repudiated her, and thereupon taken Herodias, even in her husband's lifetime, a circumstance in connection with which he had had John the Baptist put to death. Consequently there was war between Herod and Aretas on account of the wrong done the daughter of Aretas. Being sharply attacked, Herod's troops were defeated, thanks to the help of the brave Armenians; as if, by divine providence, vengeance was taken for the death of John the Baptist.
 Chapter xxix.