Indeed, al-Mansūr, al-Mahdī, and al-Rashīd—the foremost Abbasid caliphs—used to favor the scholars of the Hijaz and their opinions over the scholars of Iraq, just as the Umayyad caliphs favored the scholars of the Hijaz over those of Syria. When some of them departed from this course and turned instead to Eastern opinions, innovations multiplied among them and the caliphate weakened.
Baghdad attained its standing in knowledge and faith, and its preeminence over other cities, only after the death of Mālik and his peers among the scholars of the Hijaz. It became home to men who spread the Sunnah there and made the truths of Islam manifest, such as Ahmad ibn Hanbal, Abū Ubayd, and other jurists among the scholars of hadith. From that time onward, the Sunnah flourished there in both doctrinal foundations and practical rulings, becoming widespread and spreading from Baghdad to other cities. From that time, it also spread throughout the East and the West. Thus, the East had such scholars as Ishāq ibn Ibrāhīm ibn Rāhawayh and his companions, as well as the companions of Abd Allāh ibn al-Mubārak. The knowledge of the scholars of Medina also reached the West through what the scholars of hadith transmitted to its people. Consequently, Baghdad, Khurasan, and the West came to possess knowledge whose like was not then found in the Hijaz or Basra.
As for the state of the Hijaz, after the age of Mālik and his companions, none of its scholars surpassed the scholars of the East, Iraq, and the West.