Musnad Ahmad 28:321

Waki’ narrated to us, Khalifa ibn Khayyat narrated to me, from ‘Amr ibn Shu’ayb, from his father, from his grandfather, that the Prophet, peace and blessings of Allah be upon him, said in his sermon while he was leaning his back against the Kaaba: "The blood of the Muslims is equal in value, and the lowest of them strives for their protection [dhimmah], and they are a united hand against those who are other than them."