At the end of an “Office (Akolouthia) for St Gregory of Decapolis”, Matthew of Myra explains why he wrote it. According to his testimony, the Metropolitan arrived in Wallachia during the reign of Radu Șerban, and was appointed abbot of Dealu Monastery. Shortly after, the Transylvanian prince Gabriel Báthory invaded and pillaged Wallachia. Hidden in a cave near Bistrița monastery, together with the monks and the relics of St Gregory of Decapolis, Matthew writes an office in the saint’s honour. Soon after, Șerban returns with a new army and defeats Báthory. These events took place in 1610-1611; therefore, the “Memorandum” dates from 1611.
Österreichische Nationalbibliothek | Vindob. Suppl. gr. 90, f. 19v
The “Office (Akolouthia) for St Gregory of Decapolis” can also be found in an autograph manuscript of Matthew of Myra held in Jerusalem, in the Library of the Greek-Orthodox Patriarchate (Πατριαρχικὴ Βιβλιοθήκη Ἱεροσολύμων – ms. 161, ff. 69 sq.).