Messenger of Allah 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.  

نَهَى رَسُولُ اللَّهِ ﷺ أَنْ يُجَصَّصَ الْقَبْرُ وَأَنْ يُقْعَدَ عَلَيْهِ وَأَنْ يُبْنَى عَلَيْهِ  

It was narrated from Abu Sa’eed that the Prophet ﷺ forbade building structures over graves.  

أَنَّ النَّبِيَّ ﷺ نَهَى أَنْ يُبْنَى عَلَى الْقَبْرِ  

"The Messenger of Allah forbade plastering over graves." (Using translation from Nasāʾī 2029)   

نَهَى رَسُولُ اللهِ ﷺ أَنْ تُجَصَّصَ الْقُبُورُ أَوْ يُبْنَى عَلَيْهَا  

[Machine] The Messenger of Allah ﷺ forbade facing both Qiblas (Kaaba in Mecca and Al-Aqsa Mosque in Jerusalem) while defecating or urinating.  

نَهَى رَسُولُ اللهِ ﷺ أَنْ تُسْتَقْبَلَ الْقِبْلَتَانِ بِغَائِطٍ أَوْ بَوْلٍ  

"do not sit on graves." (Using translation from Nasāʾī 2045)   

أَنَّهُ سَمِعَ رَسُولََ اللهِ ﷺ يَقُولُ لَا تَقْعُدُوا عَلَى الْقُبُورِ  

"The Messenger of Allah forbade building over graves, making them larger or plastering over them." (One of two narrators) Sulaiman bin Musa added: "Or writing on them." (Using translation from Nasāʾī 2027)   

«نَهَى رَسُولُ اللَّهِ ﷺ أَنْ يُبْنَى عَلَى الْقَبْرِ أَوْ يُجَصَّصَ أَوْ يَقْعُدَ عَلَيْهِ وَنَهَى أَنْ يُكْتَبَ عَلَيْهِ»  

“The Messenger of Allah ﷺ forbade writing anything on graves.” (Using translation from Ibn Mājah 1563)   

«نَهَى رَسُولُ اللَّهِ ﷺ أَنْ يُبْنَى عَلَى الْقَبْرِ»