Sahih Bukhari · Hadith 4003
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi) - كتاب المغازى
حدثنا مسلم، حدثنا شعبة، عن أبي إسحاق، عن البراء، قال استصغرت أنا وابن، عمر.
Narrated Al-Bara: I and Ibn `Umar were considered too young to take part in the battle of Badr.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).