Abd Al-Razzaq’s area of specialization was the Hadith discipline, which he helped to perfect. Numerous Hadith scholars traveled to meet him and learn from him. His knowledge of Hadith was extensive. He wrote several books, the most important one of which is Al-Mussannaf, which is a collection of Hadiths in several volumes. The title means The Classified, which suggests the nature of this Hadith collection, as it is arranged according to the topics of Fiqh. His other works include a commentary on the Qur’an and a book on the Prophet’s life. However, only Al-Mussannaf survives, and has been published more than once. A new and fuller edition was published by Dar Al-Kutub Al-Ilmiyah in Beirut in 2000. This edition benefits from the fact that the editor was able to refer to three manuscripts which complement each other to provide a full copy of the book, as each manuscript suffers from the loss of some pages. It also benefits from an earlier edition published in 11 volumes.