time about twelve years old. Days after that, Abbas and Ali supported Muhammad's weight on their shoulder, as Muhammad was too weak to walk unaided. 632–634: Abu Bakr's era Inheritance from Muhammad Ibn 'Abbas was thirteen years old when Muhammad died. After Abu Bakr came to power, Ibn Abbas and his father were among those who unsuccessfully requested part of Muhammad's inheritance. Abu Bakr said that he had heard Muhammad say that prophets do not leave inheritance behind as a divine rule. Continued education After Muhammad's era, he continued to collect and learn Muhammad's teaching from Muhammad's companions (), especially those who knew him the longest. He would consult multiple Sahaba to confirm narrations, and would go to as many as thirty Companions to verify a single matter. Once he heard that a Sahaba knew a hadith unknown to him. In addition to his own scholarship, Ibn Abbas was a teacher. His house from where he taught became the equivalent of a university. One of his companions described a typical scene in front of his house: He held classes on one single subject each day. His classes covered topics such as tafsir, fiqh, Halal and Haraam, ghazawa, poetry, Arab history before Islam, inheritance laws, Arabic language and etymology. 634–644: Umar's era Advising Umar Umar often sought the advice of Ibn Abbas on important matters of state and described him as a "young man of maturity": The Sahaba Sa`d ibn Abi Waqqas said: 656–661: Ali's era Battle of Siffin Ibn Abbas remained a staunch supporter of the fourth Caliph Ali ibn Abi Talib, during Ali's war with Muawiyah, including at the Battle of Siffin. He had also been given the position of governor of Basra during Ali's reign as Caliph. A large group of Ali's army were discontented with the outcome of Ali's war with Muawiyah, and broke off into a separate group that became known as the Khawarij or Kharijites. Ibn Abbas played a key role in convincing a large number of them to return to Ali; 20,000 of 24,000 according to some sources. He did so using his knowledge of Muhammad's biography, in particular, the events of the Treaty of Hudaybiyyah. 680–683: Yazid's era Sunnis believe that ibn Abbas was in favour of the unity of the Muslims and hence did not revolt against rulers. He advised Husayn ibn Ali against his proposed expedition to Kufa that ended at