Sa'd ibn Ubadah
It is mentioned in Seerat Ibn e Ishaq (the first biography of Muhammad)) and subsequently Seerat Ibn e Hatham (another authentic biography of Muhammad)) and all other history and biography books that when Muhammad died, companions of Prophet were busy in their final rituals then they were informed that there is a gathering of Ansar of Medina. They are discussing succession after Prophet, and Sa'd ibn Ubadah chief of Khazraj clan is a strong candidate for succession of leadership. Fearing of civil war Abu Bakr, Umar and Abu Ubaidah ibn al-Jarrah instantly reached there, the situation was quite tense. Ansars were almost agreed on the khilafat of Sa'd ibn Ubadah, Muhajirs mainly above three shaikhs disagreed then Habab ibn Mundhir who was motivating the Ansars to take control of the city, suggested to appoint to two Khalifas, one from Ansars and other for Muhajirs and if Muhajirs don't agree on that term then "take your swords and throw them out of Medina". Then Bashir ibn Sa'ad who belonged to clan of Banu Aws, intervened and handled the flared up situation. He said, "O Ansar you're the first who helped Prophet when His own people rejected him, now you should not be the first to destroy unity of Muslims after Him. And whatever you'he done for Islam you should seek its reward in afterlife and should not be divided on the issue of succession."