ابن خلكان
According to Ibn Khallikan, he began his religious career with the cultivation of the religious sciences, becoming both a respected scholar of hadith and fiqh and a popular preacher in Baghdad. He was so brilliant a jurisprudent that he became the Marja of his time for all scholars in that field. He was known in Baghdad, the center of Islamic knowledge, in Isfahan, Bukhara, Samarqand, Khwarazm, and throughout Central Asia.