Muwatta Imam Malik Book of Jihad, Hadith 11

Yahya related to me from Malik that he had heard that Umar ibn Abd al-Aziz wrote to one of his governors, "It has been passed down to us that when the Messenger of Allah ﷺ sent out a raiding party, he would say to them, 'Make your raids in the name of Allah in the way of Allah. Fight whoever denies Allah. Do not steal from the booty, and do not act treacherously. Do not mutilate and do not kill children.' Say the same to your armies and raiding parties, Allah willing. Peace be upon you."

وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عُمَرَ بْنَ عَبْدِ الْعَزِيزِ، كَتَبَ إِلَى عَامِلٍ مِنْ عُمَّالِهِ أَنَّهُ بَلَغَنَا أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ إِذَا بَعَثَ سَرِيَّةً يَقُولُ لَهُمُ " اغْزُوا بِاسْمِ اللَّهِ فِي سَبِيلِ اللَّهِ تُقَاتِلُونَ مَنْ كَفَرَ بِاللَّهِ لاَ تَغُلُّوا وَلاَ تَغْدِرُوا وَلاَ تُمَثِّلُوا وَلاَ تَقْتُلُوا وَلِيدًا وَقُلْ ذَلِكَ لِجِيُوشِكَ وَسَرَايَاكَ إِنْ شَاءَ اللَّهُ وَالسَّلاَمُ عَلَيْكَ " .