 Another account also cited that the tabaqat format became popular during the period of early "hadith" transmitter critics, emerging amid the effort to identify, classify, and evaluate transmitters in the discipline known as "ilm al-rijāl".The "Tabaqat" literature were written as tools to assist the muhaddiths in their efforts to classify "hadith" transmitters and to determine the quality of particular isnads.The isnad as a system for authenticating the memory of the prophetic period required righteous, honest, and competent transmitters in every generation.