Aggai was a 1st-century primate of the Church of the East, and a disciple of Mar Addai, who is believed to have sat from 66 to 81.
Mar Addai, the traditional apostle of Mesopotamia, appointed him his successor shortly before his death.
This man used to weave Chinese cloth for Abgar, and after the death of his master Addai fled into the East.
He began to preach throughout Persia, Assyria, Armenia, Media, Babylonia and in the region of Khuzistan and among the Geles, right up to the borders of India.
Then he returned to Edessa, as he was afraid that the faith there might decline, because of the native superstition of Abgar's son, who had succeeded him as king.