It is narrated from Ata, Tawus, Mujahid, and Hasan (may Allah have mercy on them) that the Prophet ﷺ said in his sermon in the year of the conquest of Makkah: "A Muslim will not be killed in retaliation for a disbeliever." It was asked whether this narration is Mursal, so I said: Yes.
Hadith Referenceمسند الإمام الشافعي / كتاب القتل والقصاص والديات والقسامة / 1627