It is narrated from Abu Nadrah (Munzir bin Malik) that when Abu Salamah came to Basra, I and Sayyiduna Hasan (may Allah be pleased with him) went to him. He asked Sayyiduna Hasan (may Allah be pleased with him): "Are you Hasan? In Basra, there is no one I wished to meet more than you, and this is because I have learned that you issue fatwas based on your own opinion. (Therefore, listen:) Do not issue any fatwa based on your own opinion. If there is something in the Sunnah of the Messenger of Allah (peace and blessings be upon him) or in the Holy Qur'an, then mention only that."