I heard Saad bin Abu Waqqas say, "I am the first man to shed blood in the cause of Allah, and I am the first man to shoot an arrow in the cause of Allah. I remember going on raids with a band of the companions of Muhammad ﷺ when we had nothing to eat but the leaves of trees and the hubla pods, so that one of us would relieve himself like a sheep or a camel droppings without any moisture. And now the tribe of Banu Asad have taken to instructing me about religion. If that were true, I would indeed be lost and my deeds would have come to nothing."
حدثنا عمر بن إسمعيل بن مجالد بن سعيد حدثنا أبي عن بيان
سمعت سعد بن أبي وقاص يقول إني لأول رجل أهراق دما في سبيل الله وإني لأول رجل رمى بسهم في سبيل الله ولقد رأيتني أغزو في العصابة من أصحاب محمد ﷺ ما نأكل إلا ورق الشجر والحبلة حتى إن أحدنا ليضع كما تضع الشاة أو البعير وأصبحت بنو أسد يعزروني في الدين لقد خبت إذا وضل عملي
Sourcing, [sahih]. Baghawi also reported it in Sharh al-Sunnah, no. 3923, from the hadith of Tirmidhi, with the same chain.Amr bin Ismail is discarded (matruk), as stated in Tahdheeb and elsewhere. The hadith has corroborating witnesses, including the hadith that follows.