Sahih Muslim
The Book of Jihad and Expedition (Kitab Al-Jihad wal-Siyar)
Book Number: 019 / Hadith Number: 4462
It has been narrated on the authority of Umm 'Atiyya, the Ansarite, who said: I took part with the Messenger of Allah (may peace be upon him) in seven battles. I would stay behind in the camp of men, cook their food, treat the wounded and nurse the aick.