Sayyiduna Anas bin Malik (may Allah be pleased with him) narrated that Sayyidah Umm Salamah (may Allah be pleased with her) said: O Messenger of Allah, may I go out with you on the military expedition? He (peace and blessings be upon him) said: "O Umm Salamah, jihad has not been made obligatory upon women." She said: I will dress the wounds of the injured, treat eye ailments, and give water to drink. He (peace and blessings be upon him) said: "Then that is fine."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 736