Language:
كتاب الأطعمة
70  
Food, Meals
(23)
Chapter: What the Prophet (saws) and his Companions used to eat.
(23)
باب مَا كَانَ النَّبِيُّ صلى الله عليه وسلم وَأَصْحَابُهُ يَأْكُلُونَ
Sahih al-Bukhari 5412

Narrated Sa`d:

I was one of (the first) seven (who had embraced Islam) with Allah's Messenger (ﷺ) and we had nothing to eat then, except the leaves of the Habala or Hubula tree, so that our stool used to be similar to that of sheep. Now the tribe of Bani Asad wants to teach me Islam; I would be a loser and all my efforts would be in vain (if I learn Islam anew from them).

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، حَدَّثَنَا وَهْبُ بْنُ جَرِيرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ إِسْمَاعِيلَ، عَنْ قَيْسٍ، عَنْ سَعْدٍ، قَالَ رَأَيْتُنِي سَابِعَ سَبْعَةٍ مَعَ النَّبِيِّ صلى الله عليه وسلم مَا لَنَا طَعَامٌ إِلاَّ وَرَقُ الْحُبْلَةِ ـ أَوِ الْحَبَلَةِ ـ حَتَّى يَضَعَ أَحَدُنَا مَا تَضَعُ الشَّاةُ، ثُمَّ أَصْبَحَتْ بَنُو أَسَدٍ تُعَزِّرُنِي عَلَى الإِسْلاَمِ، خَسِرْتُ إِذًا وَضَلَّ سَعْيِي‏.‏
Reference : Sahih al-Bukhari 5412
In-book reference : Book 70, Hadith 40
USC-MSA web (English) reference : Vol. 7, Book 65, Hadith 323
  (deprecated numbering scheme)