The article is devoted to the linguotextual study of the translated Life of Saint Athanasius the Athonite and the identification of the basic principles of lexical editing found in the copies of the δ text group of the First Edition of the source. The Greek original and 15 Slavic copies of the 14th-16th centuries of the First Edition of the Life helped to characterise the lexical substitutions attested in the copies of the δ text group. By using the material of the Second Edition of the Life in the “Sobornik” by Nilus of Sora, it is shown how significantly the editing principles differ in the texts of the δ group of the First Edition and in Nilus’ edition. Firstly, in the texts of the δ group, lexical substitutions are sporadic and are not conditioned by the belonging of words to the linguistic tradition of any book school, while Nilus gives preference to ancient Ohridisms and eliminates pre-Slavicisms. Secondly, the creator of the prototype of the δ text group, when correcting archaisms for frequently used lexemes, selects partial synonyms, unlike Nilus, who uses exact equivalents. A common feature of the lexical editing of the δ group texts of the First Edition and Nilus’ edition is the desire to adapt the original text for the perception of a scribe of the late 15th - early 16th centuries by reflecting the progressive changes in the lexical norm of the literary Slavonic language in the language of the Life.