"Asmā' ar-rijāl" is a term used by scholars of Hadīth.
Hadīth is a body of Islamic literature that consists of reports of the sayings, actions, and approvals of the Prophet Muhammad and his companions. The term "Asmā' ar-rijāl" refers to the biographical study of the individuals who transmitted Hadīth, such as the Companions of the Prophet, their students, and the generations that followed them.
The aim of this study is to establish the reliability and credibility of the narrators, as the authenticity of a Hadīth depends on the trustworthiness of its transmitters. Thus, the biographical study of the narrators is crucial in determining the authenticity of a Hadīth and its acceptance as evidence in Islamic law.