It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Medina is a sanctuary from the mountain of 'Ayr to the mountain of Thawr. Whoever introduces an innovation in Medina or gives refuge to an innovator, upon him is the curse of Allah, the angels, and all people. Allah will not accept any obligatory or voluntary act of worship from him on the Day of Resurrection."