Abu Ya?la Mu?ammad ibn al-?usayn Ibn al-Farra? (April 990 – 15 August 1066), commonly known as al-Qa?i Abu Ya?la or simply as Ibn al-Farra?, was a prominent Hanbali scholar and one of the early Muslim jurists who played dynamic roles in formulating a systematic legal framework and constitutional theory on Islamic system of government during the first half of the 5th/11th Century in Baghdad.