Abū l-Faḍl Dāʾūd b. Sulaymān Ibn Abī l-Bayān al-Isrāʾīlī (d. c.634/1236) was a physician and pharmacologist who had a distinguished career at the Ayyūbid court in Cairo. He was a Jewish Karaite, an adherent of a movement that denied the authority of the rabbinic tradition, and he was a pupil of Ibn Jumayʿ (or Ibn Jāmiʿ, d. 594/1198), a Jewish physician in the service of the sultan al-Malik al-Nāṣir Ṣalāḥ al-Dīn (Saladin; r. 567-89/1171-93). Like his master, Ibn