Ibrahim al-Nakha'i, may Allah have mercy on him, in the explanation of the verse: "And it is not for a believer to kill a believer except by mistake," said: When a Muslim mistakenly kills another Muslim whose heirs are Muslims, then the blood money is given to them; and if that Muslim belongs to a people who are your enemies, then only a neck (slave) is to be freed for him, because his heirs are polytheists and they have no treaty with the Messenger of Allah, peace and blessings be upon him; and if that Muslim belongs to a polytheist people with whom the Muslims have a treaty, then the blood money is given to his polytheist heirs because they are responsible for his blood money, and his inheritance will go to the Muslims.
Hadith Referenceسنن سعید بن منصور / كتاب التفسير / 664
Hadith Gradingمحدثین:سنده ضعيف لأن مغيرة لم يصرح بالسماع بينه وبين إبراهيم.
Hadith Takhrij«أخرجه سعيد بن منصور فى (سننه) برقم: 664، 2828، وابن أبى شيبة فى (مصنفه) برقم: 28580، 34116»