This paper describes a Judeo-Arabic genizah fragment, BUD GEN 210+, and discusses the implications of its discovery. The fragment was originally part of an anthology on physics that included writings by Ibn Sīnā and Ibn Rushd. One page contains the end of a book of Physics (al-samāʿ al-ṭabīʿī), which two colophons ascribe to Abraham Ibn Daud, the Jewish philosopher of Toledo (ca. 1110–1180). The manuscript is significant in itself, as a witness to an unknown work by Ibn Daud and as the sole surviving specimen of his Arabic writing. In addition, it lends definitive support to the hypothesis, advanced sixty years ago by Marie-Thérèse d’Alverny, that Avendauth, the twelfth-century Toledan Jewish translator of Ibn Sīnā from Arabic into Latin, should be identified with Abraham Ibn Daud.