The Messenger of Allah ﷺ said, "Whoever performs an action that is not in accordance with our way, it is rejected."
أن رسول الله ﷺ قال: من عمل عملا ليس عليه أمرنا فهو رد.
Muslim narrated it in the Book of Judgments (18:1718) through the route of Abu Amir Abdul-Malik bin Amr (he is Aqdi), who said, Abdullah bin Jafar Zuhri narrated to us, from Saad bin Ibrahim who said, I asked Qasim bin Muhammad about a man who had three dwellings and bequeathed a third of each dwelling. He said, "All of that is combined into one dwelling." Then he said, "Ayesha told me," and he mentioned it.The legal opinion of Qasim bin Muhammad is not binding, for it is permissible for the heirs to designate one part, namely the third, from each house for the legatee, just as it is permissible for them to appraise the three houses and pay out a third of the value to the legatee. Qasim bin Muhammad then traced back what he had heard from Ayesha, the hadith mentioned, and it has no bearing on his legal opinion.As for the hadith, it points to two matters. The first is a warning against introducing innovations into the religion. The second is acting upon an introduced innovation. His saying, "then it is rejected," means it is turned back, meaning that both introducing something into the religion and acting upon an innovation are rejected, and both the one who introduces it and the one who acts upon it are sinful.