Qadi Abu Yusuf was a descendent of the Ansar and Sahaba Hadrat Sa'd b. Sibat. Born in Kufa in 113 or 117 H and passed away on the 5th of Rabi' al-Awwal 182 H. Muhammad b. al-Hasan al-Shaibani was born in 135 H and passed away in 189 H. He attended for about 2 yrs the lectures of Imam Abu Hanifah Radi Allahu anhu, and upon the latter's death, he completed his education under Abu Yusuf. He also studied for 3 yrs the Muwatta of Imam Malik Radi Allahu anhu under the great Imam himself, in Medina.
Qadi Abu Yusuf as long as Imam Abu Hanifah Radi Allahu anhu lived, he regularly attended his court. Imam Abu Hanifah acknowledged his mastery in Fiqh. Returning once from a visit to Abu Yusuf during the latter's sickness, Abu Hanifah Radi Allahu anhu said to his companions:
"If, Allah forbid, this man (Abu Yusuf) dies, the world will lose one of its great scholars."
Abu Yusuf attended the lectures of many other doctors. He heard Traditions from A'mash, Hisham b. 'Urwah, Sulaiman Taimi, Abu Ishaq Shaibani, Yahya b. Sa'id al-Ansari and others, learned maghazi (military history) and siyar (biography) from Muhammad b. Ishaq and knowledge of Fiqh from Muhammad b. Abi Laila. Allah endowed him with so much intelligence and such a good memory that he learned all these disciplines simultaneously! Other Imams in other sciences ackowledged his quick intelligence and penertration.
Although he is known mostly in Fiqh, he was unrivalled in other sciences.The historian Ibn Khallikan quotes Hilal b. Yahya as having said: "Abu Yusuf was a hafiz of tafsir (exegesis), maghazi and ayyam al-'Arab (history of Arabia), Fiqh was one of his minor accomplishments."
- Abu Yusuf was ranked so high in Hadith so as to be counted huffaz in it, the famous and strict muhhadith Dhahabi included an account of Abu Yusuf in his Tadhkirat al-Huffaz.
- Ahmad Hanbal Radi Allahu anhu said "When I was first attracted to Hadith, I went to Abu Yusuf.
- Muzni, a famous disciple of Shafi'i Radi Allahu anhu used to say: "Abu Yusuf follows more Hadith than anybody else. 'Abd al-Barr, a well-known Muhaddith, writes that Abu Yusuf used to visit different Muhaddithin and at one sitting learn 50 to 60 Traditions, all of which he would retain in his memory!
- A'mash the famous muhaddith having consulted Abu Yusuf on a question, said on hearing his reply: "Have you any authority for this?". "Yes", replied Abu Yusuf, and he reminded A'mash of a Tradition which the latter had narrated to him on a certain occasion. "Ya'qub", said A'mash, "I first heard this Tradition when your parents had yet not got married, but I have understood its meaning only today" (Ibn Khallikan, Ta'rikh, note on Abu Yusuf).