Note of guidance about the fasts and feasts of the Christians
Date: Unknown; before 1048
Original Language: Arabic
The work has not survived, and the title is only known from al-Bīrūnī's own bibliography, which he attached to the list of the works of al-Rāzī; see al-Bīrūnī, Risāla fī fihrist kutub Muḥammad ibn Zakariyāʾ al-Rāzī, ed. M. Mohaghegh, Tehran, 1985, p. 32, no. 53.
It can be assumed that the contents did not significantly add…