On the day of Pentecost, among the many nations present were "Parthians and Medes and Elamites and dwellers in Mesopotamia." Eusebius traced missionary work in what was Parthia to the Apostle Thomas. Another arguably less reliably tradition is that of Addai of Edessa. There is hard evidence of Christians in what was by then the Sasanian Empire around 233, namely the Domus Ecclesiae (house-converted-into-a-church) at Dura Europos . In second half of the third century, there was a bishop of Seleucia-Ctesiphon by the name of " Papa/Pappa ". During this Sasanid period (dating from 224), the Church spread throughout the Persian Empire. The churches used the Syriac language. A representative of the church in the Sasanian Empire was present at the 325 Council of Nicea, and was called " John of Persia ". There was a 40-year persecution lasting 339 to 379 under Shapur II (309–79). One contemporary Christian whose writings record these events was the theologian ...