Ilm ar-Rijal

Biographical evaluation (Arabic: عِلْمُ الرِّجال‎, translit. `Ilm al-Rijāl‎), literally meaning 'Knowledge of Men' but more commonly understood as the Science of Narration, refers to a discipline of Islamic religious studies within hadith terminology in which the narrators of hadith are evaluated. Its goal is to distinguish authentic and reliable hadiths from unreliable hadiths in establishing the credibility of the narrators, using both historic and religious knowledge.`Ilm ar-rijal is synonymous with what is commonly referred to as al-jarḥ wa al-taʻdīl (discrediting and accrediting) – the criticism and declared acceptance of hadith narrators.

Ali ibn al-Madini, an early authority on the subject, said, "Knowing the narrators is half of knowledge."

In his Introduction to the Science of Hadith, Ibn al-Salah, a renowned hadith specialist, explained the importance of the study of hadith narrators. Introducing the chapter entitled, 'Recognizing the trustworthy, reliable narrators and those who are weak and unreliable,' Ibn al-Salah said, "This is from the most distinguished and noble types (of hadith study) as it results in recognizing the authenticity of a hadith or its weakness." He then explained that any criticism directed at a narrator was permissible due to the "maintenance of the Shariah, purging it of any mistakes or misinformation".

Stressing the importance of biographical evaluation, Ali ibn al-Madini, an early authority on the subject, said, "Knowing the narrators is half of knowledge."

...
Wikipedia