Kufa was considered as a major centre for Hadith Sciences from the time Caliph 'Umar (d.24 A.H.) sent 'Abd Allah ibn Mas'ud (d.32 A.H.), the sixth person to embrace Islam, as a tutor to the people of Kufa. The approximate number of students who attended ibn Mas'ud's discourses were 4,000. Besides ibn Mas'ud, there were other illustrious companions of the Prophet (SAW) who resided in Kufa, prominent among them being Abu Musa al-Ash'ari (d.52 A.H.), Salman al-Farsi (d.35 A.H.), 'AmmAr b. Yasir (d.37 A.H.), Huzaifa b. Yaman (d.35 A.H.) and S'ad b. Abu Waqqas (d.55 A.H.). Therefore, on one occasion referring to Kufa, 'Ali b. Abu Talib (d.40 A.H.), the fourth Caliph of Islam remarked, "The companions of ibn Mas'ud are the lanterns of this Umma (Muslim community)". Since the famous traditionists were stationed in Kufa, Imam Bukhari said that he cannot even count how often he accompanied the traditionists to Kufa and Baghdad.