In this scholarly treatise, Muhammad ibn Qasim al-Hasani al-Fasi addresses a critical topic in Islamic jurisprudence: the ruling on acting upon weak (da'if) hadith. The author meticulously defends the position that it is prohibited to intentionally act upon weak narrations, even for matters concerning virtues of deeds (fadā'il al-a'māl). He systematically refutes the arguments of those who permit it under certain conditions, thereby lifting the blame and censure from scholars who adopt the stricter view. This book is an essential resource for students of hadith sciences and Islamic law, providing a detailed analysis of the principles of hadith authentication and its practical application.