Prohibition of Plastering and Building over the Graves

Imam Al-Nawawi’s Riyad-us-Saliheen
Chapter 348
Prohibition of Plastering and Building over the Graves

1767. Jabir (May Allah be pleased with him) said: The Messenger of Allah (sallallaahu ’alayhi wa sallam) forbade that the graves should be plastered (made into permanent structures), used as sitting places (for the people) or building over them.
[Muslim].