Someone asked Ali, "Did the Prophet of Allah ﷺ entrust to you anything that he did not entrust to people in general?"Ali replied, "No, except for what is in this document of mine."He then took out a document from the sheath of his sword, and in it was written, "The believers are equal in their blood. They stand united against all others, and the protection granted by the least of them is binding on them all. No believer is to be killed in retaliation for a disbeliever, nor is anyone under a covenant to be killed while his covenant stands. Whoever commits a crime bears its consequences himself, and whoever shelters a criminal, upon him is the curse of Allah, the angels, and all people."
أخبرني محمد بن المثنى قال حدثنا يحيى بن سعيد قال حدثنا سعيد عن قتادة عن الحسن عن قيس بن عباد قال انطلقت أنا والأشتر إلى
هل عهد إليك نبي الله ﷺ شيئا لم يعهده إلى الناس عامة قال لا إلا ما كان في كتابي هذا فأخرج كتابا من قراب سيفه فإذا فيه المؤمنون تكافأ دماؤهم وهم يد على من سواهم ويسعى بذمتهم أدناهم ألا لا يقتل مؤمن بكافر ولا ذو عهد بعهده من أحدث حدثا فعلى نفسه أو آوى محدثا فعليه لعنة الله والملائكة والناس أجمعين
[Sahih] Reported by Abu Dawud, Diyat, chapter "Should a Muslim be executed for killing a disbeliever?", no. 4530, from the hadith of Yahya bin Saeed Qattan, with this chain, and it is also in Al-Kubra, no. 6936. Saeed here is Ibn Abu Aruba, and there are two defects in it, at 34 and 36. It has corroborating narrations in Bukhari, no. 3047 and 6915, and Ibn Hibban, no. 1699, and others. Al-Hafiz graded it hasan in Al-Fath, 12/231, and the author of Al-Tanqih graded it sahih.