The letter concerns Bishop Dorotheus of Thessalonica. The papal legates were passing through his city in their way to Constantinople in 519 and asked him to sign the libellus of faith drawn up in Rome (the pope demanded its acceptance it from the bishops wishing to enter communion with Rome; it included, among others, the condemnation of Eutyches and Nestorius, the full acceptance of the council of Chalcedon in 451, and the Tome of Leo). Dorotheus refused to sign the libellus without the gathering of the local bishops. The legates, already in Constantinople, sent one of them, Bishop John and the Presbyter Epiphanius to Thessaloniki. Dorotheus, however, resolved on not signing the libellus and disturbed the people of the city. Dorotheus sent to Bishop John and the Presbyter Epiphanius his presbyter, Aristides, with two bishops declaring that the libellus needs corrections, but the envoys refused to make any. The next day they were attacked by the mob. The case was brought to the emperor who promised to punish the guilty. When Hormisdas learnt about those events, he dispatched a letter to his legates in which he asked them to persuade the emperor to send Dorotheus and Aristides to Rome. The present letter is the response. For the legacy to Constantinople in 519, and the events in Thessaloniki see the lettters 185, 186, 225, 226 in the Collectio Avellana and Vasiliev 1950: 168-197.