Musnad Ahmad 1617

It was narrated that Qais said: I heard Sa"d bin Malik say: By Allah, I was the first of the Arabs to shoot an arrow for the sake of Allah. We used to go out on campaign with the Messenger of Allah (ﷺ) and we would have no food except the leaves of al-hubah and as-samur (desert trees), and one of us would produce stools like a sheep, so dry that nothing stuck to it. And now Banu Asad are teaching me about my religion, in which case I must have been doomed and my efforts wasted