Sayyiduna Jarir (may Allah be pleased with him) said: the Messenger of Allah (peace and blessings be upon him) sent a detachment (sariyyah) to Khath'am, and some of them tried to seek protection by prostrating, but (the detachment) hastily killed them. News of this reached the Prophet (peace and blessings be upon him), so he ordered half the blood money for them and said: "I am free of every Muslim who lives among the polytheists." The people said: O Messenger of Allah, why? He said: "The fires of the two should not be visible to one another (that is, they should keep apart from them)."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2251