The Prophet ﷺ said, "The believers are equal in the value of their blood. They stand united against all others, and the protection granted by the least among them is binding on them all. A believer is not to be killed in retaliation for a disbeliever, nor is one bound by a covenant to be killed during the term of his covenant."
أخبرني أبو بكر بن علي قال حدثنا القواريري قال حدثنا محمد بن عبد الواحد قال حدثنا عمرو بن عامر عن قتادة عن أبي حسان
أن النبي ﷺ قال المؤمنون تكافأ دماؤهم وهم يد على من سواهم يسعى بذمتهم أدناهم لا يقتل مؤمن بكافر ولا ذو عهد في عهده
[Sahih] Reported by Abu Yaala in his Musnad, 1/424, no. 302, and Abdullah bin Ahmad in Zawaid al-Musnad, 1/122, both of them from Ubaydullah bin Umar Qawariri, with the same chain. It also appears in al-Kubra, no. 6937. The hadith has many corroborating narrations, including the preceding hadith.Abu Hassan is Muslim bin Abdullah Aaraj. In al-Sunan al-Sughra and al-Kubra he is named Amr bin Amir, but the correct reading is Umar bin Amir, as given in Tuhfat Ashraf and Tahdhib al-Tahdhib and other sources. See the coming hadith numbered 4749.