عَنِ ابْنِ عَبَّاسٍ رَضِيَ اللَّهُ عَنْهُمَا قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ إِذَا بَعَثَ جُيُوشَهُ، قَالَ: ((اخْرُجُوا بِسْمِ اللَّهِ، تُقَاتِلُونَ فِي سَبِيلِ اللَّهِ مَنْ كَفَرَ بِاللَّهِ، لَا تَغْدِرُوا، وَلَا تَغُلُّوا، وَلَا تُمَثِّلُوا، وَلَا تَقْتُلُوا الْوِلْدَانَ وَلَا أَصْحَابَ الصَّوَامِعِ))
It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with him) that when the Messenger of Allah (peace and blessings be upon him) would dispatch his armies, he would say: Set out in the name of Allah, fight in the way of Allah against those who disbelieve in Allah, do not deceive, do not be treacherous, do not mutilate, and do not kill children or the people of churches.