It has been narrated on the authority of Anas b. Malik who said that the Messenger of Allah ﷺ allowed Umm Sulaim and some other women of the Ansar to accompany him when he went to war;
they would give water (to the soldiers) and would treat the wounded.

حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا جَعْفَرُ بْنُ سُلَيْمَانَ، عَنْ ثَابِتٍ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ كَانَ رَسُولُ اللَّهِ ﷺ يَغْزُو بِأُمِّ سُلَيْمٍ وَنِسْوَةٍ مِنَ الأَنْصَارِ مَعَهُ إِذَا غَزَا فَيَسْقِينَ الْمَاءَ وَيُدَاوِينَ الْجَرْحَى .