Musnad Ahmad 32:1142

Yazid narrated to us, Humayd informed us, from Anas, that his uncle was absent from the battle of Badr. He said: "I was absent from the first battle the Prophet, may God bless him and grant him peace, fought against the polytheists. If God lets me witness a battle against the polytheists, God shall surely see what I will do." When the day of Uhud came, the Muslims were routed. He said: "O God, I apologize to You for what these have done"—meaning his companions—"and I disassociate myself from what these have brought"—meaning the polytheists. Then he advanced, and Sa'd met him at the rear, before Uhud—and Yazid said in Baghdad: "at the rear, before Uhud." Sa'd said: "I am with you." Sa'd said: "I could not do what he did." They found on him eighty-odd wounds, between a strike of a sword, a thrust of a spear, and a shot of an arrow. He said: "We used to say that regarding him and his companions was revealed: 'Among the believers are men true to what they promised God. Among them is he who has fulfilled his vow [to the death], and among them is he who awaits [his chance].'" [Al-Ahzab: 23]