Second son of Michael ibn Daud (No. 4); born in Seville about the middle of the eleventh century; lived in Lucena, where he devoted himself to philosophy and theology. He married Miriam, a daughter of Isaac ben Judah ibn Ghayyat (or ibn Giat), and sister of Judah ibn Ghayyat, who influenced his studies; and he enjoyed the advantage of close association with Alfasi. Into his circle came also the young Judah ha-Levi, then a student at the Lucena college. Hai is said to have been the author of some writings on the Talmud and of a work on philosophy. He wrote also a brief commentary on the Megillot. He had four sons, Michael, Isaac, Enoch, and Joseph, who lived in Lucena and Cordova until the invasion of the Almohades caused them to go to Tudela in 1146.