Is it Permissible to Build a Masjid Over a Prophet's or a Scholar's grave ?

What is understood from the wording of the question is that the prohibition of taking graves as Masjids came in the Qur'an, because he (i.e., the questioner) said: "Verily Allah instructs the believers to avoid…" So, his question makes it seem that this is in the Qur'an. However, the matter is not as he thought, if he actually thought that. This is not in the Qur'an, but the Prophet ﷺ cursed those who take the graves as Masjids. This was stated in the Sunnah. And there is no doubt that taking the graves as Masjids is a major sin. However, if there is a grave in a Masjid: If the Masjid is built upon the grave, it must be demolished and removed. And if the grave has been placed in the Masjid after it had already been built, it must be taken out of the Masjid. So, the ruling is given to the first of the two. If the Masjid was built first, the grave would be removed. And if the grave was there first, then the Masjid would be demolished. And it is not permissible to build Masjids upon graves, and it is not permissible for the dead to be buried in the Masjids. And this does not include what many people found problematic in regard to the grave of the Prophet ﷺ and the two graves of his companions, which are in the Masjid of the Prophet ﷺ. That’s because the Masjid was not built on them. The Masjid used to be separate. And this was the room of Aisha, may Allah be pleased with her, where the Prophet ﷺ was buried and where he died. Abu Bakr chose to be buried with him and similarly Umar, may Allah be pleased with both of them. And the story of Umar in regard to confirming with Aisha in that matter (i.e., being buried there) is famous. I say: this [ruling] does not apply to their case, because this house (Aisha’s) was distinct and separate from the Masjid. And neither the Prophet ﷺ nor his two companions were buried in the Masjid, nor was it built over them. However, at the time of Al-Waleed and over 90 years after the Hijrah (migration of the Prophet ﷺ), the Masjid needed to be expanded. So, the leaders at that time added the houses of the wives of the Prophet ﷺ to it. And among them is Aisha's house, but the house remained separate and distinct from the Masjid in its structure; While some people at that time disapproved of this matter and did not agree with it. The people of Ilm (Islamic knowledge) have mentioned that most of the Companions, may Allah pleased with them, were not present at that time in Madinah. Those who were present from the Companions at that time were dispersed in the newly conquered lands of Islam. Based on this, the issue of including the house into the Masjid was not a matter of agreement among the people at that time, but it remained so and was never changed. That’s because changing it is difficult. So, they kept it as it is. However, it is – and all praise is to Allah – separate from the Masjid, distinct from it. Neither the graves were ever placed inside the Masjid, nor was the Masjid built over them.