Musnad Abu Ya'la al-Mawsili 117:26

Narrated to us ‘Abd al-Wahid ibn Ghiyath Abu Bahr, narrated to us Hammad, narrated to us Thabit, from Anas: That the wives of the Prophet, may Allah bless him and grant him peace, used to go out in the darkness of the night with water skins, giving water to the companions of the Messenger of Allah, may Allah bless him and grant him peace.