It is narrated from Sayyiduna Amr bin Awf bin Milhah al-Muzani (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever takes as patrons others than his true patrons, upon him will be the curse of Allah and His wrath on the Day of Resurrection; Allah will not accept from him any voluntary or obligatory act of worship. Whoever kills someone other than the one who tried to kill him, upon him will be the curse of Allah and His wrath on the Day of Resurrection; Allah will not accept from him any voluntary or obligatory act of worship. And whoever introduces a new thing (an innovation) or gives shelter to an innovator, upon him will be the curse of Allah and His wrath on the Day of Resurrection; Allah will not accept from him any voluntary or obligatory act of worship."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14107