Musnad Abu Ya'la al-Mawsili 133:18

Abu Bakr ibn Abi Shaybah narrated to us, Shadhan narrated to us, Hammad ibn Salamah narrated to us, from Thabit and Ali ibn Zayd, from Anas: That when the polytheists overwhelmed the Messenger of Allah (may Allah bless him and grant him peace) on the day of Uhud, he said, "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 another stood up to repel them until he was killed, [continuing] until seven were killed. The Messenger of Allah (may Allah bless him and grant him peace) said, "Our companions have not treated us fairly."