Sahih Bukhari Volume 8, Book 81, Hadith 6455

حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنْ إِسْمَاعِيلَ، حَدَّثَنَا قَيْسٌ، قَالَ سَمِعْتُ سَعْدًا، يَقُولُ إِنِّي لأَوَّلُ الْعَرَبِ رَمَى بِسَهْمٍ فِي سَبِيلِ اللَّهِ، وَرَأَيْتُنَا نَغْزُو، وَمَا لَنَا طَعَامٌ إِلاَّ وَرَقُ الْحُبْلَةِ وَهَذَا السَّمُرُ، وَإِنَّ أَحَدَنَا لَيَضَعُ كَمَا تَضَعُ الشَّاةُ، مَا لَهُ خِلْطٌ، ثُمَّ أَصْبَحَتْ بَنُو أَسَدٍ تُعَزِّرُنِي عَلَى الإِسْلاَمِ، خِبْتُ إِذًا وَضَلَّ سَعْيِي‏.‏

Narrated By Sa'd : I was the first man among the Arabs to throw an arrow for Allah's Cause. We used to fight in Allah's Cause while we had nothing to eat except the leaves of the Hubla and the Sumur trees (desert trees) so that we discharged excrement like that of sheep (i.e. unmixed droppings). Today the (people of the) tribe of Bani Asad teach me the laws of Islam. If so, then I am lost, and all my efforts of that hard time had gone in vain.