This 18th-century manuscript offers a clear example of the continued use in the Islamic world of the scientific commentary well after the end of Middle Ages, the period most associated with Arabic scientific achievement and this literary form. In this case, the treatise commented upon is the Nuzhat al-Nuẓẓār fī ‘ilm al-Ġubār (The excursion of the observer in the science of numerals), which was itself an abridgment by Aḥmad ibn Muḥammad al-Farāḍī ibn al-Hā'im (around 1356-1412) of his own mathematical treatise entitled Muršida al-Ṭālib ilā Asnā al-Maṭālib (A student guide to the summit of learning). The original work, the abridgement, and the commentary all have an explicit didactic aim. The discussion of numerals and the treatment of the four arithmetical operations are presented in an incremental and extremely clear way. Abridgments, commentaries, and supercommentaries (commentaries on commentaries) all were tools for clarifying complex mathematical problems to students in an accessible and detailed form. The present copy of the Kitāb Šarḥ Nuzha fī ‘Ilm al-Ḥisāb demonstrates very clearly Aḥmad ibn Qāsim al-Šhāfi‘ī al-Ġhazzī ’s explanatory technique: the passages in red ink preserve the original treatise by Ibn Al-Hā'im, while the text in black ink is the extremely detailed, almost word-by-word, commentary by al-Ġhazzī.