ENOfficial
Narrated Al-Bara: I and Ibn `Umar were considered too young to take part in the battle of Badr.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُسْلِمٌ، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي إِسْحَاقَ، عَنِ الْبَرَاءِ، قَالَ اسْتُصْغِرْتُ أَنَا وَابْنُ، عُمَرَ.
sunnah.com