that a woman was found killed in one of the expeditions of the Prophet (may Allah's peace and blessings be upon him), and so the Messenger of Allah (may Allah's peace and blessings be upon him) denounced killing women and boys

عَنْ عَبْدِ اللَّهِ بنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُما: أَنَّ امْرَأَةً وُجِدَتْ فِي بَعْضِ مَغَازِي النَّبِيِّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ مَقْتُولَةً، فَأَنْكَرَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ قَتْلَ النِّسَاءِ وَالصِّبْيَانِ.