The Holy Symeon was bishop of the royal cities of Seleucia and Ctesiphon in Persia, during a great persecution under King Sapor II. The king had been incited by (Zoroastrian) Magi jealous of the growth of the Faith in their territory, and by some Jews living in Persia. The king was already displeased with the holy bishop: his eunuch, Ustazan, a secret Christian, had denied Christ, but when reprimanded by Symeon, had confessed the Faith before the King, for which he was executed. On Holy Friday of 343 Symeon, along with at least a hundred other servants of the Church, was sent out to be slain. Symeon exhorted each to be of good courage, and was himself slain last. One year later, again on Holy Friday, the King's eunuch Azat was executed for Christ, along with a great number of the faithful. It is said that more than 1,000 Christians died as martyrs during this persecution.

The Zoroastrians still live in parts of Iran as a small, somewhat persecuted minority under the Islamic government.