The Messenger of Allah ﷺ said, "Whoever introduces a good practice that is then acted upon will have its reward and a reward equal to that of everyone who acts upon it, without anything being diminished from their rewards. And whoever introduces an evil practice that is then acted upon will bear its sin and the sin of everyone who acts upon it after him, without anything being diminished from their sins."
حدثنا محمد بن عبد الملك بن أبي الشوارب حدثنا أبو عوانة حدثنا عبد الملك بن عمير
قال رسول الله ﷺ من سن سنة حسنة فعمل بها كان له أجرها ومثل أجر من عمل بها لا ينقص من أجورهم شيئا ومن سن سنة سيئة فعمل بها كان عليه وزرها ووزر من عمل بها من بعده لا ينقص من أوزارهم شيئا
Muslim narrated it in Zakat, chapter on encouragement to give charity etc., hadith no. 1017, in the section on knowledge, from Muhammad bin Abdul-Malik and others through him.