The study deals with the so far unexplored manuscript of a prayer called Molitva o izbavljenii otъ blǫda, which is preserved in the manuscript collection from the Kirillo-Belozersky Monastery (White Lake St. Cyril’s Monastery). The text of the prayer is preserved in the manuscript KB 12/1089 (National Library of Russia, Saint-Petersburg) from the third quarter of the 16th century. The close relationship of known manuscript versions of the prayer contained in the manuscripts of Czech Church Slavonic Forty Gospel Homilies by Pope Gregory the Great (Besědy na evangelije) and in the ancient Euchologium Sinaiticum strongly reinforces the hypothesis about the Great Moravian origin of their common archetype. The aim of the study is to reveal the relationship of the newly registered text KB 12/1089 to familiar texts. An integral part of the study also deals with an edition of the prayer (KB 12/1089) and its critical apparatus based on the text of all known (edited) manuscripts of the prayer.