The Messenger of Allah ﷺ said, "Whoever introduces into this affair of ours something that is not part of it, it is rejected."
حدثنا إسحاق بن عيسى قال حدثني عبد الله بن جعفر الزهري من آل المسور بن مخرمة عن سعد بن إبراهيم عن القاسم بن محمد
قال رسول الله ﷺ من صنع أمرا من غير أمرنا فهو مردود
Its isnad is sahih. Muhammad bin Isa is the brother of Ishaq bin Isa al-Tabbaa, and he is among the trustworthy scholars of hadith and jurisprudence, and his hadith is found in the Sunan works. The hadith will come later with the wording "whoever performs an act" at 25348. It was narrated by Bukhari 5/310 no. 2697 in the chapter on reconciliation, Muslim 3/1343 no. 1718 in the chapter on judgments, Abu Dawud 4/200 no. 4606 in the chapter on sunnah, and Ibn Majah 1/7 no. 14 in the introduction.