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
Letters of the Living Abjad numerals system the letters of the Arabic alphabet are assigned numerical values. The Arabic letters h ح and y ي, which compose the Arabic singular adjective meaning "living" in the phrase Letters of the Living, add up to 18, and therefore the phrase "Letters of the Living" refers to the number 18. There is a similar symbolism about the numerical value of the corresponding Hebrew word in Judaism. The Báb referred to the 18 Letters of the Living, along with himself, as the first "Váḥid" of the Bayán Dispensation. In the Abjad numerical value of the word Wáḥid (واحد)