(85) باب فَضْلِ الْمَدِينَةِ وَدُعَاءِ النَّبِيِّ صلى الله عليه وسلم فِيهَا بِالْبَرَكَةِ وَبَيَانِ تَحْرِيمِها وَتَحْرِيمِ صَيْدِهَا وَشَجَرِهَا وَبَيَانِ حُدُودِ حَرَمِهَا
Abu Huraira (Allah be pleased with him) reported Allah's Apostle (ﷺ) as saying:
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.
Reference: Sahih Muslim 1371 a
In-book reference: Book 15, Hadith 534
USC-MSA web (English) reference(deprecated numbering scheme): Book 7, Hadith 3166