Sahih al-Bukhari 3956

Arabic

حَدَّثَنِي مَحْمُودٌ، حَدَّثَنَا وَهْبٌ، عَنْ شُعْبَةَ، عَنْ أَبِي إِسْحَاقَ، عَنِ الْبَرَاءِ، قَالَ اسْتُصْغِرْتُ أَنَا وَابْنُ عُمَرَ يَوْمَ بَدْرٍ، وَكَانَ الْمُهَاجِرُونَ يَوْمَ بَدْرٍ نَيِّفًا عَلَى سِتِّينَ، وَالأَنْصَارُ نَيِّفًا وَأَرْبَعِينَ وَمِائَتَيْنِ‏.‏

English translation

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

Reference: Sahih al-Bukhari 3956, Book of Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi). English translation by Dr. Muhammad Muhsin Khan.