Sahih Bukhari, Chapter: Jihaad (Fighting for the cause of Allah)

On the day (of the battle) of Uhad when (some) people retreated and left the Prophet (SAW), I saw Aisha bint Abu Bakr and Um Sulaim, with their robes tucked up so that the bangles around their ankles were visible (This event took place before the revelation of the Verses of Hijab [veiling], Fath-al-Bari Vol.6) hurrying with their water skins (in another narration it is said, "carrying the water skins on their backs"). Then they would pour the water in the mouths of the people, and return to fill the water skins again and came back again to pour water in the mouths of the people.