He narrated from the Prophet Muhammad (S.) excessively. The six Sahih books of Hadith and the rest of the Sunni books quoted from him much many traditions. In front of this large number of traditions, we had no way but to research on their sources, because they concerned our religious and mental life directly. Otherwise we would turn away from them and their narrator to take care of something more important.
But these numerous traditions spread into the branches and fundamentals of the religion that made all the Sunnis of the four sects and the Ash’arites and their lecturers trust in and depend upon when dealing with the Shari’ah. So there was no way save to research on the narrator himself and his traditions to be certain about the laws of Allah (S.w.T.) and His Shari’ah.