Musnad Abu Ya'la al-Mawsili 6:44

Zuhayr narrated to us, Waki’ narrated to us, from Ibn Abi Khalid, from Qays ibn Abi Hazim, who said: I heard Sa’d saying: "I am indeed the first man among the Arabs to shoot an arrow in the way of Allah. And I have seen us with the Messenger of Allah (may Allah bless him and grant him peace) while we had no food except the *samur* (acacia leaves) and the leaves of the *hablah* (a type of tree). So much so that one of us would defecate just as a goat defecates, having no mixture."