As hadith, which records words and actions attributed to the Prophet Muḥammad, became a scriptural source in Muslim legal-ritual discourses, hadith criticism, which examines the authenticity of a hadith and the reliability of narrators involved in its transmission, flourished in the ninth century, when hadith critical works were written or compiled. Among the ninth-century contributors to hadith criticism, Ibrāhīm b. Yaʿqūb al-Saʿdī al-Jūzjānī (d. 259/873?) authored the first work exclusively dedicated to evaluation of hadith transmitters, but remains obscure and understudied in modern hadith scholarship. By closely analyzing the organizational structure of his surviving work, Aḥwāl al-rijāl, his use of hadith critical terminology, and his methodological innovation, this paper suggests that al-Jūzjānī’s approach to hadith criticism can be characterized as unconventionally intolerant of non-Sunnī sectarians but paradoxically influential on hadith scholarly literature. Departing from the earlier hadith critics, who did not consistently consider extrinsic factors such as sectarian tendencies in their evaluation of hadith transmitters, al-Jūzjānī systematically integrates “religious orthodoxy” into the framework of hadith criticism by employing morally judgmental terms and impugning hadith transmitters’ credentials on account of their religious “deviation”, which is presented by al-Jūzjānī as equally detrimental as mendacity to the preservation of authentic hadith. Although al-Jūzjānī’s harsh judgments on hadith transmitters with mild Shīʿī tendencies were often rejected by later hadith critics and led to the Nāṣibī accusation, this paper argues that his approach nonetheless informs the disciplinary development of hadith criticism and even precipitates the introduction of “moral uprightness” (ʿadāla) into its conceptual framework.