Musnad Ahmad Hadith 1966

Najdah al-Haroori wrote to Ibn "Abbas to ask him about killing boys; who the khumus belongs to; when a child is no longer to be regarded as an orphan; whether women accompanied any campaign or took part in fighting; and whether slaves had any share of the booty. Ibn "Abbas wrote to him (saying): As for boys, if you are al-Khadir and could tell disbelievers apart from believers, then (go ahead) and kill them; as for the khumus, we used to say that it is for us but our people said that it is not for us; as for women, the Messenger of Allah (ﷺ) used to take women with him so they could treat the sick and take care of the wounded, but they did not take part in fighting; as for the child, he is no longer regarded as an orphan when he reaches puberty; as for slaves, they had no share of the booty but they would be given something.