The Third Slavonic Life of St. Nahum of Ochrid is known only from two editions arranged by P. A. Lavrov. The only manuscript burnt down during the World War II in the National Library in Beograd. The text is very close to the Short Greek Life of St. Nahum, but it is not an exact translation of it (there are several differences). The Slavonic Life was probably translated from Greek in the 17th or 18th century. This short hagiography has a strong polemic dimension, the polemic against Latin Church arises especially in the Filioque question. The author or the compiler of the original text used more sources. Some of them are very old, certainly written before 13th century, as they have a very positive relation to the Roman pope, who is perceived in the whole text as very positive. Especially the description of the imprisonment and miraculous liberation of Method's disciples is overlain with similar biblical events from the Acts of Holy Apostles. There is a very interesting passage, where the author says, that disciples in prison sung the troparion of the third hour at noon. This is not a mistake. Disciples prayed in the prison. In the 9th century there were two forms of horologion in Byzantine rite - monastic. The question which of these two forms was used by cyrillo-methodian mission remains open. This service was celebrated only during the Great Lent, so according to this we can specify the date of expulsion of Method's disciples from Great Moravia, which happened during the Great Lent of 886 (between 20th February and end of March).