About the Mystery of the Letters the mid-6th century, in which Mar Saba had played an important role. The anonymous author of the treatise declares he was prompted to the study of the secret meanings of the letters by the words of the Apocalypse, "I am the Alpha and Omega", and that he subsequently received a vision about them on Mount Sinai. The author proposes a re-modelled Greek alphabet reduced to 22 letters on the model of the 22 letters of Hebrew (discounting Xi Ξ and Psi Ψ), and with the Hebrew letter names. He then interprets these letters as symbolic figures of 22 works of
Hebrew alphabet "dagesh kal", also modifies the sounds of the letters ב, כ and פ in modern Hebrew (in some forms of Hebrew it modifies also the sounds of the letters ג, ד and/or ת; the "dagesh chazak" – orthographically indistinguishable from the "dagesh kal" – designates gemination, which today is realized only rarely – e.g. in biblical recitations or when using Arabic loanwords). "alef", ע "ayin", "vav" and "yod" are letters that can sometimes indicate a vowel instead of a consonant (which would be, respectively, ). When they do, and are considered to constitute part of the vowel designation in combination