The Compendium of Knowledge and Wisdom

Zayn an-Din 'Abd ar-Rahman ibn Ahmad ibn 'Abd ar-Rahman (known as Rajab) ibn al-Hasan ibn Muhammad ibn Abi'l-Barakat Mas'ud al-Baghdadi ad-Dimashqi al-Hanbali (736-795 AH). Rajab was the nickname of his grandfather 'Abd ar-Rahman, perhaps because he was born in that month. Born in Baghdad, Ibn Rajab learned much from his father, who himself was a great scholar, and then studied in Egypt and Damascus where he settled down until he died. Among his eminent teachers were Abu'l-Fath Muhammad ibn Muhammad ibn Ibrahim al-Mayduni, Muhammad ibn Isma'il al-Khabbaz, Ibrahim ibn Dawud al-Attar, Abu'l-Haram al-Qalanisi, and Imam Ibn Qayyim al-Jawziyyah. He was a colleague of the famous hadith expert Al-Hafiz Abu'l-Fadhl al-Iraqi. He devoted himself to the subject until he became an expert in all the sciences related to hadith. He then taught hadith and fiqh according the Hanbali school in the Jami' Bani Umayyah and other seats of learning in Damascus.His famous students include scholars like Abu'l-Fadhl Ahmad ibn Nasr ibn Ahmad, the Mufti of Egypt (d. 844 AH), Dawud ibn Sulayman al-Mawsili (d. 844 AH). He was a leading scholar of the Hanbali school. His work al-Qawa'id al-Kubra fi al-Furu' is clear evidence of his expertise in fiqh, demonstrating an extreme, even exhaustiveknowledge of the intricacies of detailed fiqh issues. He was known for piety and righteousness. His sermons were considered most effective, full of blessing and beneficial. People of all schools were unanimous as to his quality, and hearts of the people were full of love for him. He was not involved in any worldly business, nor did he visit people of material position. He wrote a detailed 20-Volume scholarly commentary on the Sunan at-Tirmidhi, a commentary on part of Sahih al-Bukhar, a Dhayl (supplement) to Tabaqat al-Hanabilah, al-Lata'if fi wasa'if al-ayyam, Bayan fadl 'ilm as-Salaf 'ala al-Khalaf.

Among his best known most referenced works is Jami' al-'Ulum wa al-Hikam, the commentary on al-Arba'un (the forty hadith) of Imam Nawawi. He added eight hadith to the original 42 and commented in detail on all of these fifty hadith. This commentary discusses all aspects of the hadith, the chain of narrations, the narrator and the text.

Hafiz Ibn Hajar al-'Asqalani said of him, ''He was a great expert in the sciences of hadith-the historical accounts of narrators, the chains of narrations, and meaning of the text.