Karaite scholar flourished in the ninth century. He was called "the teacher of the diaspora," and esteemed for his brilliant intellect. None of his works has survived but many of them are known by quotations made by Karaite writers. Solomon b. Yeruḥam, in his "Muḳaddimah" (Introduction to the Decalogue), mentions Baḥtawi's "Sefer ha-Miẓwot" (Book of Precepts) and Jephet ben Ali in his commentary upon the Book of Daniel refers to Baḥtawi's Biblical commentaries. Baḥtawi was known chiefly as "ha-medaḳdeḳ" (the grammarian), and his etymologies are quoted by the Karaite lexicographer David b. Abraham Alfasi. Bacher identifies him with Abu Ya'aḳub Joseph ben Noah, but this is questioned by Poznanzki.