This volume presents the first English translation of Imām Abū al-Qāsim al-Qushayrī’s Kitāb al-Arbaʿīn fī Taṣḥīḥ al-Muʿāmala (The Book of Forty Ḥadīths on the Rectification of Conduct), a classic collection devoted to the cultivation of character and spiritual refinement. Comprising fifty-six Prophetic reports arranged across forty thematic chapters, the work addresses foundational virtues such as repentance, sincerity, remembrance of Allah, humility, patience, and reliance upon Him. This bilingual edition features the complete Arabic text with full vocalization alongside an English translation of both the chains of transmission (isnāds) and the narrations themselves, together with source documentation (takhrīj), paragraph numbering, explanatory notes, a glossary of key terms, and comprehensive indices.