Not the Apostle Jude The Mission to Abgar

Thaddeus, called Addai in the Syriac tradition, was a Jew of Edessa by origin and came to Jerusalem for a feast. He heard the preaching of John the Forerunner, was baptized, and afterward followed Christ, and was numbered among the seventy whom the Lord sent out ahead of Him two by two.

The story attached to his name is the story of Abgar the Fifth, called Ukkama, the Black, king of Osrhoene, whose capital was Edessa on the far eastern edge of the Roman world. Eusebius, writing early in the fourth century, says he found the documents in the public record office of Edessa, in Syriac, and translated them: a letter from the king to Jesus, and a reply.

The king, in the letter as Eusebius gives it, has heard of the healings, believes the healer to be either God or the Son of God, invites Him to come to Edessa, and offers Him the shelter of a small city out of reach of the Jerusalem authorities. The reply blesses him for believing without having seen and says that the mission must be finished first, and that afterward one of the disciples will be sent to heal him.