He early distinguished himself in the learning of traditions by heart, and when, in his sixteenth year, his family made the pilgrimage to Mecca, he gathered additions to his store from the authorities along the route. Already, in his eighteenth year, he had devoted himself to the collecting, sifting, testing and arranging of traditions. For that purpose he travelled over the Moslem world, from Egypt to Samarkand, and learned (as the story goes) from over a thousand men three hundred thousand traditions, true and false. He certainly became the acknowledged authority on the subject, and developed a power and speed of memory which seemed miraculous, even to his contemporaries. His theological position was conservative and anti-rationalistic; he enjoyed the friendship and respect of Abmad Ibn Uanbal. In law, he appears to have been a Shafi'ite.
After sixteen years' absence he returned to Bokhara, and there drew up his Hadith, a collection of 7275 tested traditions, arranged in chapters so as to afford bases for a complete system of jurisprudence without the use of speculative law, the first book of its kind (see Islamic Law). He died in A.ll. 256, in banishment at Kartank, a suburb of Samarkand. His book has attained a quasi-canonicity in Islam, being treated almost like the Koran, and to his grave solemn pilgrimages are made, and prayers are believed to be heard there.