I heard the Prophet ﷺ forbid sitting on a grave, plastering it, or building over it.
حدثنا عبد الرزاق حدثنا ابن جريج أخبرني أبو الزبير أنه سمع
سمعت النبي ﷺ ينهى أن يقعد على القبر وأن يقصص أو يبنى عليه
Its isnad is sahih. Nasai narrated it 4/86 no. 2027, in the chapter on funerals, on the prohibition of plastering graves, and Ibn Majah 1/498 no. 1564 narrated something similar, and Ibn Abu Shayba 3/335 narrated something similar, and Hakim graded it sahih 1/370. Dhahabi agreed with him.