Mar Rav Hai, son of Mar Rav David, was Rosh Yeshiva in Pumbedita from the year 4648 for seven years and a half [(Tzed"h). The Sheftei Yeshanim wrote that it is explained in Sefer Yetzirah that he composed the book Kol HaShem BeKoach and the book HaKemitza; I do not know from where he derived that this Rav Hai composed them].