Sufyan al-Tammar narrates that he saw the blessed grave of the Prophet (peace and blessings be upon him) shaped like a camel's hump.
If the report of al-Qasim bin Muhammad (may Allah have mercy on him) is authentic, that their graves were spread with the gravel of the courtyard, this indicates that they were level; and since Sufyan al-Tammar's seeing the blessed grave of the Prophet (peace and blessings be upon him) humped is also authentic, it seems it was changed from how it was originally.
For its wall fell in the time of al-Walid bin Abd al-Malik, and it is said in the time of Umar bin Abd al-Aziz (may Allah have mercy on him), and then it was repaired.
The hadith of al-Qasim bin Muhammad (may Allah have mercy on him) in this chapter is more authentic and more likely to be the preserved one. However, some of the scholars among our companions (the Shafi'is) considered making the grave humped preferable in this time, since it is permissible by consensus, and because levelling has become a mark of the people of innovation, so that it does not become a cause for tongues to wag about the deceased and for him to be accused of the innovators' doctrines of which he is free. And success is from Allah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6761