Abu Marthad Kannaz bin Husain (May Allah be pleased with him) said:
I heard the Messenger of Allah (ﷺ) saying: "Do not offer Salat (prayer) facing the graves and do not sit on them."[Muslim]. (JA)
App reference (JA): Book 18, Hadith 247 (JA)
Arabic/English book reference (JA): Book 18, Hadith 1757 (JA)