Musnad Abu Ya'la al-Mawsili 117:45

Hadaba narrated to us, Hammad narrated to us, from Thabit, from Anas, that the Messenger of Allah (peace and blessings of Allah be upon him) said on the day of Uhud, when they overwhelmed him while he was with seven of the Ansar and two men from the Quraysh: "Who will repel them from us, and he will be my companion in Paradise?" A man from the Ansar stood up and fought until he was killed. Then he said the same thing, so another stood up and fought until he was killed. He continued to say the same thing until the seven were killed. Then the Messenger of Allah (peace and blessings of Allah be upon him) said: "Our companions have not treated us fairly."