Messenger of Allah ﷺ said, "If somebody innovates something which is not in harmony with the principles of our religion, that thing is rejected."  

قَالَ رَسُولُ اللَّهِ ﷺ: «مَنْ أَحْدَثَ فِي أَمْرِنَا هَذَا مَا لَيْسَ فِيهِ فَهُوَ رَدٌّ۔»  

He who innovates things in our affairs for which there is no valid (reason) (commits sin) and these are to be rejected.  

قَالَ رَسُولُ اللَّهِ ﷺ: «مَنْ أَحْدَثَ فِي أَمْرِنَا هَذَا مَا لَيْسَ مِنْهُ فَهُوَ رَدٌّ۔»  

I asked Qasim b. Muhammad about a person who had three dwelling houses and he willed away the third part of every one of these houses; he (Qasim b. Muhammad) said: All of them could be combined in one house; and then said: 'A'isha informed me that Messenger of Allah ﷺ said: He who did any act for which there is no sanction from our behalf, that is to be rejected.  

سَأَلْتُ الْقَاسِمَ بْنَ مُحَمَّدٍ عَنْ رَجُلٍ لَهُ ثَلاَثَةُ مَسَاكِنَ فَأَوْصَى بِثُلُثِ كُلِّ مَسْكَنٍ مِنْهَا قَالَ: يُجْمَعُ ذَلِكَ كُلُّهُ فِي مَسْكَنٍ وَاحِدٍ۔ ثُمَّ قَالَ: أَخْبَرَتْنِي عَائِشَةُ أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ: «مَنْ عَمِلَ عَمَلاً لَيْسَ عَلَيْهِ أَمْرُنَا فَهُوَ رَدٌّ۔»