Hadith 6:965
Hafs narrated to us, from Ibn Jurayj, from Abu al-Zubayr, from Jabir, who said: The Messenger of Allah (may Allah bless him and grant him peace) forbade that a grave be plastered with gypsum, that one sit upon it, and that a structure be built over it.
حدثنا حفص عن بن جريج عن أبي الزبير عن جابر قال نهى رسول الله صلى الله عليه وسلم أن يجصص القبر وأن يقعد عليه وأن يبنى عليه