Musnad Ahmad 5:473

'Abd al-Rahman narrated to us, from Sufyan, from al-A'mash, from Ibrahim al-Taymi, from his father, from 'Ali, who said: We have nothing except the Book of Allah the Exalted, and this scroll from the Prophet, may Allah bless him and grant him peace: "Al-Madinah is a sanctuary between 'A'ir and Thawr. Whoever commits an innovation (hadath) in it, or shelters an innovator (muhdith), upon him is the curse of Allah, the angels, and all of mankind. Neither a ransom (adl) nor a substitution (sarf) will be accepted from him." And he said: "The protection (dhimmah) of the Muslims is one; whoever violates the protection of a Muslim, upon him is the curse of Allah, the angels, and all of mankind. Neither a substitution nor a ransom will be accepted from him." "And whoever takes as guardians a people without the permission of his own masters, upon him is the curse of Allah, the angels, and all of mankind. Neither a substitution nor a ransom will be accepted from him."