Umayr ibn Abi Waqqas (RA) was still very young at the time of the battle of Badr, but he wanted to fight. So he was afraid that Rasulullah (PBUH) might stop himfrom fighting so he hid himself among the grown men. Prophet Muhammad (PBUH) saw him and stopped him from going with the army. Young Umayr (RA) could not bear this so he started crying, because he wanted to fight in the cause of Allah - even though he was young. When the Prophet (PBUH) heard this, he permitted him.
His brother, Sa'd (RA) said:
"The sword of Umayr was too big for his size. I had to put a number of knots in the belt, so that it might not touch the ground"
This article was culled from the publications of Deen Communication Limited