It is narrated that Sayyiduna Amr bin Awf bin Milhah al-Muzani (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever revives a Sunnah of mine that has been made to die out after me, he will have a reward equal to that of all the people who act upon it, without that diminishing anything from the people's rewards. And whoever invents an innovation that Allah and His Messenger are not pleased with, upon him will be a sin equal to that of all the people who act upon that innovation, without that diminishing anything from the people's sins."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14082