Hadith 4:171
Abu Marthad al-Ghanawi reported God’s messenger as saying, “Do not sit on graves, and do not pray facing them.” Muslim transmitted it.
وَعَنْ أَبِي مَرْثَدٍ الْغَنَوِيِّ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «لَا تَجْلِسُوا عَلَى الْقُبُورِ وَلَا تُصَلُّوا إِلَيْهَا» . رَوَاهُ مُسْلِمٌ
Original Reference: Mishkat al-Masabih 1698