The ruling on building Structures over the Graves and writing on them

Question :

I noticed that with us on some of the graves are cement slabs that are made approximately a meter in length and half a meter in width. On these slabs is written the name of the deceased, the date of his death and some sentences, like: "O Allâh, have mercy on so-and-so, the son of so-and-so," and so forth. So what is the ruling on this practice?

Answer:

It is not permissible to build structures on graves; nor cement slabs or anything else. It is also not permissible to write on them due to what is confirmed from the Prophet of the prohibition of building structures over graves and writing on them. Muslim recorded a Hadith from Jabir in which he said:

"The Messenger of Allah prohibited plastering the grave, sitting on it and building structures over it."

At-Tirmithi and others reported this same Hadith with an authentic chain of narration and he added: "And he (the Prophet) also prohibited that it be written on." Because this is a type of exaggeration, it is obligatory to prevent it. Also, writing (on the graves) might lead to wicked consequences, such as exaggeration and other things that are forbidden Islamically. The only thing that should be done is returning the dirt of the grave back onto it and elevating it approximately a hand's span so that it will be known that it is a grave. This is the Sunnah regarding the graves that the Messenger of Allâh and his Companions used to follow. It is also not permissible to establish Masjids over graves, dress them with covering cloth, nor to place domes (or shrines) over them. This is due to the statement of the Prophet:
"May Allah curse the Jews and the Christians. They took the graves of their Prophets as Masjids."

This Hadith's authenticity is agreed upon.

This is also due to what Muslim recorded in his Sahih from Jundub bin 'Abdullah Al-Bajali. He said: "I heard the Messenger of Allah saying five days before he died:
'Verily, Allah took me as a Khalil (intimate companion) just as he took Ibrahim as a Khalil. If I had taken a Khalil from my Ummah, I would have taken Abu Bakr as a Khalil. Verily, those before you all used to take the graves of their Prophets and righteous people as Masjids. Do not take the graves as Masjids, for verily I forbid you all from that."
The Hadiths with this meaning are numerous.

Source:
Ash-Shaykh Ibn Baz
Fatawa Islamiyah, Vol. 3 Pages 85-86