Musnad Abu Ya'la al-Mawsili 3:36

Ubayd Allah ibn Umar narrated to us, Abd al-Rahman narrated to us, Sufyan narrated to us, from al-A’mash, from Ibrahim al-Taymi, from his father, from Ali, who said: We have nothing except the Book of Allah and this scroll from the Prophet, may Allah bless him and grant him peace, that he said: "Indeed, Medina is sacred from ‘A’ir to Thawr. Whoever commits an innovation (hadath) in it or harbors an innovator, upon him is the curse of Allah, the angels, and all of mankind; neither a mandatory act (sarf) nor a supererogatory act (adl) will be accepted from him." And he said: "The protection (dhimmah) of the Muslims is one; the lowest of them strives to uphold it. Whoever violates the protection of a Muslim, upon him is the curse of Allah, the angels, and all of mankind; neither a mandatory act nor a supererogatory act will be accepted from him." "And whoever attaches himself to a people without the permission of his masters (mawali), upon him is the curse of Allah, the angels, and all of mankind; Allah will not accept from him a mandatory act nor a supererogatory act."