The book is an analytical commentary (sharh) by Dr. Labib Najib Abd-Allah on the classical collection known as al-Arbain fi al-Ahkam (The Forty Hadiths on Rulings) compiled by the famous 13th-century Hadith master Imam al-Mundhiri (al-Hafiz Zaki al-Din al-Mundhiri, d. 656 AH / 1258 CE).