Medina is a sacred territory, so he who made any innovation in it. or gave protection to an innovator, there is upon him the curse of Allah, that of the angels and that of all the people. There would not be accepted on the Day of Resurrection either obligatory acts or supererogatory acts from him. (Using translation from Muslim 1371a)
قَالَ رَسُولُ اللهِ ﷺ الْمَدِينَةُ حَرَمٌ فَمَنْ أَحْدَثَ فِيهَا حَدَثًا أَوْ آوَى مُحْدِثًا فَعَلَيْهِ لَعْنَةُ اللهِ وَالْمَلَائِكَةِ وَالنَّاسِ أَجْمَعِينَ لَا يَقْبَلُ اللهُ مِنْهُ يَوْمَ الْقِيَامَةِ عَدْلًا وَلَا صَرْفًا