Musnad Ahmad 8:60

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Isma'il, who said: I heard Qays ibn Abi Hazim say: Sa'd said: "I have seen myself as the seventh of seven with the Messenger of Allah, may Allah bless him and grant him peace, and we had no food except the leaves of the *hublah* (a type of desert tree), to the point that one of us would defecate just as a sheep defecates, with nothing mixed into it. Then, the Banu Asad began to rebuke me regarding Islam. If that were the case, I would have indeed lost, and my efforts would have gone astray."