بُلُوغُ الْمَرَامِ
Bulugh al-Maram 217
The Book of Prayer
وَعَنْ أَبِي مَرْثَدٍ اَلْغَنَوِيِّ - رضى الله عنه - قَالَ : سَمِعْتَ رَسُولَ اَللَّهِ - صلى الله عليه وسلم -يَقُولُ : { لَا تُصَلُّوا إِلَى اَلْقُبُورِ , وَلَا تَجْلِسُوا عَلَيْهَا } رَوَاهُ مُسْلِمٌ . [1]
Narrated Abu Marthad al-Ghanawi (RA): I heard Allah's Messenger (ﷺ) say, "Don't pray towards graves and don't sit on them." [Reported by Muslim]
Sunnah.com reference: Book 2, Hadith 81