He said to Ali, "People have been spreading rumors about what they have been hearing. If the Messenger of Allah ﷺ entrusted you with anything special, please tell us about it."Ali replied, "The Messenger of Allah ﷺ did not entrust me with anything that he did not entrust to people in general, except for what is in the sheath of my sword."He then took out a document which read, "The blood of the believers is equal in value, the lowest of them may grant protection on behalf of all, no believer shall be killed in retaliation for a disbeliever, nor shall anyone under a covenant be killed during the term of his covenant."Abridged.
أخبرنا أحمد بن حفص قال حدثني أبي قال حدثني إبراهيم بن طهمان عن الحجاج بن الحجاج عن قتادة عن أبي حسان الأعرج
أنه قال لعلي إن الناس قد تفشغ بهم ما يسمعون فإن كان رسول الله ﷺ عهد إليك عهدا فحدثنا به قال ما عهد إلي رسول الله ﷺ عهدا لم يعهده إلى الناس غير أن في قراب سيفي صحيفة فإذا فيها المؤمنون تتكافأ دماؤهم يسعى بذمتهم أدناهم لا يقتل مؤمن بكافر ولا ذو عهد في عهده مختصر
[Sahih] It is also found in Al-Kubra, hadith no. 6948, and in Juz Ibrahim bin Tahman (Mashyakhah, hadith no. 51, in full). See also the previous hadith. As for his saying "on the authority of Ashtar," it perhaps means that Ashtar said to Ali... and so on. And Allah knows best.