Sayyiduna Jarir (may Allah be pleased with him) said: the Messenger of Allah (peace and blessings be upon him) said: "Whoever introduces a good practice in Islam that is acted upon after him, there will be written for him the equivalent of the reward of those who act upon it, and nothing will be reduced from the reward of those who act upon it. And whoever introduces an evil practice in Islam that is acted upon after him, there will be written against him the equivalent of the sin of those who act upon it, without anything being reduced from their sins."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2432