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, and it is acted upon after him, will have a reward equal to the reward of those who act upon it, without anything being reduced from their rewards. And whoever introduces an evil practice in Islam, and it is acted upon after him, will bear a burden of sin equal to the sin of those who act upon it, without anything being reduced from their sins."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2429