It has long been known that Muslim scholars used rabbinic literature in what is called Isra’iliyyat in the Islamic tradition. They used these sources as legitimate details of the Qur’anic stories. Less well known is how later Islamic scholars incorporated these sources into their own retellings of the stories that all three texts—the Qur’an, the Hebrew Bible, and the New Testament—share. This article examines the hagiography by Abdülvasi Çelebi (d. 1415), Halilname, which tells the story of Abraham and draws on rabbinic literature. Several factors led to the use of Jewish sources in Halilname. First, the Ottoman state did not have a canonized orthodox Islamic system until Süleyman I (r. 1520–66), and this lack of canonization gave Islamic mystics greater liberty to say what they wanted. Second, a zeitgeist of religious syncretism drew inspiration from the mysticism that dominated Anatolia. Finally, the most important patriarch for Jews, Christians, and Muslims—Abraham—proved the ideal subject in an empire that included members of all three monotheistic religions.