Amr bin Shu'ayb narrates from his father, and he from his grandfather (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "The blood of the believers is equal, one to another, and they are as one hand against those besides them."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15904