Allah's Messenger (ﷺ) forbade that the graves should be plastered or they be used as sitting places (for the people), or a building should be built over them.
Sahih Muslim Book 11, Hadith 121
← Previous Hadith Should I not send you on the same mission as Allah's Messenger (ﷺ) sent me? Do not leave an image without obliterating it, or a high grave without levelling It. This hadith has been reported by Habib with the same chain of transmitters and he said: (Do not leave) a picture without obliterating it.

Sahih Muslim Book 11, Hadith 120 Next Hadith → A hadith like this has been transmitted on the authority of Jabir b. 'Abdullah.

Sahih Muslim Book 11, Hadith 122