أَبُو يُوسُفَ يَعقُوبُ بنُ إِبرَاهِيمَ الأَنصَارِيّ — أَبرَزُ طُلَّابِ أَبِي حَنِيفَةَ وَأَوَّلُ قَاضِي القُضَاةِ فِي العَالَمِ الإِسلَامِيِّ وَمُؤَلِّفُ كِتَابِ الخَرَاجِ وَالعَالِمُ الَّذِي جَعَلَ المَذهَبَ الحَنَفِيَّ مُهيمِنًا فِي الإِمبِرَاطُورِيَّةِ العَبَّاسِيَّة
Abu Yusuf Ya'qub ibn Ibrahim al-Ansari (أَبُو يُوسُفَ يَعقُوبُ بنُ إِبرَاهِيمَ الأَنصَارِيّ; born c. 113 AH / 731 CE in Kufa; died 182 AH / 798 CE in Baghdad; born into poverty — his family reportedly could not afford to keep him studying; Abu Hanifa personally supported him financially to continue studying; became Abu Hanifa's most trusted and distinguished student; after Abu Hanifa's death [150 AH], Abu Yusuf continued the Hanafi tradition and taught many scholars; Abbasid career: appointed chief judge [qadi] by Caliph al-Mahdi; later elevated by Caliph Harun al-Rashid to the unprecedented position of *Qadi al-Qudat* [Judge of Judges / Chief Qadi of the entire empire] — the first time in Islamic history this office was created; as Qadi al-Qudat, Abu Yusuf appointed judges throughout the Abbasid Empire and through these appointments made the Hanafi madhhab the dominant legal school of the state; his major works: [1] *Kitab al-Kharaj* [Book of Land Tax]: written at Harun al-Rashid's request; the most important classical treatise on Islamic fiscal and administrative law; addresses: land tax on conquered territories, jizya [poll tax on non-Muslims], fay' [war spoils], treatment of dhimmis; established the principle that conversion to Islam does not automatically exempt a convert from kharaj [land tax] — a politically significant ruling that had been disputed; [2] *Kitab al-Athar*: a hadith collection organized by Abu Yusuf; [3] *al-Radd 'ala Siyar al-Awza'i*: a legal polemical text defending the Hanafi position against the Syrian legal tradition; significant differences from Abu Hanifa: Abu Yusuf occasionally diverged from his teacher, particularly on issues of state administration where his experience as a judge gave him practical perspective Abu Hanifa lacked; his tenure represents the mature Hanafi school moving from scholarly circle to state institution) is the pivotal figure in the institutionalization of the Hanafi madhhab.
From Poverty to Chief Judge
Abu Yusuf’s life trajectory is one of the most remarkable in Islamic legal history. He was born into poverty in Kufa and nearly had to abandon his studies when his family could not support him. Abu Hanifa reportedly paid his living expenses so he could continue — an act of personal investment in a student that paid extraordinary dividends.
When Abu Hanifa died under Abbasid pressure (he refused to accept a judicial appointment and was imprisoned), it was Abu Yusuf who continued the school, trained a new generation of Hanafi scholars, and eventually brought the school into the heart of the Abbasid state apparatus.
Qadi al-Qudat: A New Office
The title Qadi al-Qudat (Judge of Judges) did not exist before Harun al-Rashid created it for Abu Yusuf. Before this, judges were appointed by caliphs or governors regionally. The new office centralized judicial appointments: Abu Yusuf now had authority over judicial appointments throughout the empire.
The practical consequence: within a generation, Hanafi scholars filled judicial positions from Spain to Khorasan. The Hanafi school’s legal opinions became the operative law of the Abbasid Empire. The other schools continued as scholarly traditions but not as state law.
Kitab al-Kharaj
Written at Harun al-Rashid’s request as a guide to fiscal administration, Kitab al-Kharaj addresses the most politically sensitive questions of Islamic governance: how are newly conquered lands taxed? What rights do non-Muslim subjects have? Can a converted farmer stop paying kharaj?
Abu Yusuf’s key ruling on the last question — that conversion does not automatically exempt a former kharaj-payer from land tax — preserved the Abbasid revenue base while still making it jurisprudentially defensible. It was a ruling shaped by his experience as a judge dealing with real administrative problems.
See also: Seerah Ibrahim Al Nakhai, Seerah Al Aswad Ibn Yazid Al Nakhai, Seerah Malik Ibn Anas, Seerah Samura Ibn Jundub, Seerah Jabir Ibn Abdallah Al Ansari