Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
كتاب المغازى
(6) Chapter: The number of the warriors of Badr
باب عِدَّةِ أَصْحَابِ بَدْرٍ
Narrated Al-Bara:
I and Ibn `Umar were considered too young (to take part) in the battle of Badr, and the number of the Emigrant warriors were over sixty (men) and the Ansar were over 249.