This thesis presents the earliest available treatise on "Adab al-Qädi" written by al-Khassäf (261/874). The work is the most informative and authentic Hanafite treatise relating to the principles of interpreting and administering the Shari'a law. It defines the nature and function of the administration of justice in the early Islamic period. The original work of al-Khassäf is not extant, but we have Ibn Mäza's recension of it together with his comments. The present work of Ibn Mäza is not only a recension of al-Khassäf's treatise but also an examination of the development of the subject from the death of al-Khassäf (i. e., 261/874) up to the year 500/1106. The thesis has been divided into two parts. Part I consists of a critical edition of the treatise Sharh Adab al-Qädi by Ibn Mäza. Part II includes the Introduction consisting of three sections. Section I is devoted to the study of the administration of justice in early Islam. It takes into account the ethical code and organised procedure of the early Islamic courts of law with special reference to the present work.