(33) باب النَّهْىِ عَنِ الْجُلُوسِ، عَلَى الْقَبْرِ وَالصَّلاَةِ عَلَيْهِ
Abu Marthad al-Ghanawi reported Allah's Messenger (ﷺ) as saying:
Do not sit on the graves and do not pray facing towards them.
Reference: Sahih Muslim 972 a
In-book reference: Book 11, Hadith 126
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 2121