كتاب الحج
15  
The Book of Pilgrimage
(85)
Chapter: The virtue of Al-Madinah and the Prophet's Prayer for it to be blessed. Its sanctity and the sanctity of its game and trees. The Boundaries of its sanctuary
(85)
باب فَضْلِ الْمَدِينَةِ وَدُعَاءِ النَّبِيِّ صلى الله عليه وسلم فِيهَا بِالْبَرَكَةِ وَبَيَانِ تَحْرِيمِها وَتَحْرِيمِ صَيْدِهَا وَشَجَرِهَا وَبَيَانِ حُدُودِ حَرَمِهَا
Sahih Muslim 1367

'Asim reported:

I asked Anas (Allah be pleased with him) whether Allah's Messenger (ﷺ) had declared Medina as sacred. He said: Yes, it is sacred, so its tree is not to be cut; and he who did that let the curse of Allah and that of the angels and of all people be upon him.
حَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا يَزِيدُ بْنُ هَارُونَ، أَخْبَرَنَا عَاصِمٌ الأَحْوَلُ، قَالَ سَأَلْتُ أَنَسًا أَحَرَّمَ رَسُولُ اللَّهِ صلى الله عليه وسلم الْمَدِينَةَ قَالَ نَعَمْ هِيَ حَرَامٌ لاَ يُخْتَلَى خَلاَهَا فَمَنْ فَعَلَ ذَلِكَ فَعَلَيْهِ لَعْنَةُ اللَّهِ وَالْمَلاَئِكَةِ وَالنَّاسِ أَجْمَعِينَ ‏.‏
Reference : Sahih Muslim 1367
In-book reference : Book 15, Hadith 528
USC-MSA web (English) reference : Book 7, Hadith 3160
  (deprecated numbering scheme)