The discovery by Harkavy of the "Kitab al-Riyaḍ wal-Ḥada'iḳ," by the Karaite Al-Ḳirḳisani, threw further light on David. Al-Ḳirḳisani cites a work by him on the various Jewish sects, and says that David had "embraced Christianity" (tanaṣṣar), that he was for many years the pupil of a renowned Christian physician and philosopher named Hana, and that, after acquiring considerable knowledge of philosophy, he wrote two works against Christianity which became famous. But it seems more probable that the word "tanaṣṣar" means simply that David had intercourse with Christians. Ḳirḳisani, indeed, does not mention his return to Judaism, and no Rabbinite mentions his conversion to Christianity. His conversion to Christianity can hardly be reconciled with the fact that he is cited by Baḥya, by Jedaiah Bedersi (in "Iggeret Hitnaẓẓelut"), and by Moses ibn Ezra. Ḳirḳisani mentions two other books by David: "Kitab al-Khaliḳah," a commentary on Genesis extracted from Christian exegetical works; and a commentary on Ecclesiastes. He is incorrectly mentioned as a learned Karaite by David al-Hiti in his chronicle of Karaite doctors, published by Margoliouth ("Jew. Quart. Rev." ix.432).