Is prayer valid in mosques that contain graves?

Q: The brother: M. A. N - from a recent deceased - in Dakahlia - in Egypt, says in his question: Is prayer valid in mosques that contain graves?

A: Mosques that contain graves are not to be prayed in, and it is obligatory to dig up the graves and transfer the remains to the public cemeteries, placing the remains of each grave in a separate pit like the other graves, and it is not permissible for graves to remain in mosques, whether the grave of a wali (close friend of Allah) or anyone else; because the Messenger (peace and blessings be upon him) forbade and warned against that, and he cursed the Jews and the Christians for their doing of it. It is established from him (peace and blessings be upon him) that he said: Aisha (may Allah be pleased with her) said: He warned against what they did. It is agreed upon by al-Bukhari and Muslim.
And he (peace and blessings be upon him) said, when Umm Salama and Umm Habiba informed him of a church in Abyssinia that contained images: It is agreed upon as authentic. And he (peace and blessings be upon him) said: Muslim narrated it in his Sahih, from Jundub ibn Abdullah al-Bajali.
So he (peace and blessings be upon him) forbade taking graves as mosques, and he cursed whoever did that, and he informed that they are the worst of creation, so it is obligatory to be cautious of that.
And it is known that whoever prays at a grave has taken it as a mosque, and whoever builds a mosque over it has taken it as a mosque, so it is obligatory to keep graves away from mosques, and not to place graves in them; in obedience to the command of the Messenger (peace and blessings be upon him), and in caution from the curse that came from our Lord for whoever builds mosques over graves; because if one prays in a mosque that contains graves, Satan may make it attractive to him to call upon the deceased, or seek aid from him, or pray to him, or prostrate to him, so major shirk (associating partners with Allah) occurs. And because this is from the practice of the Jews and the Christians, it is obligatory that we differ from them, and that we distance ourselves from their path, and from their evil practice.
But if the graves were old and then the mosque was built over them, it is obligatory to demolish and remove it; because it is the newly added element, as the scholars have explicitly stated; to cut off the causes of shirk (associating partners with Allah) and to block the means to it.
Here is a doubt (shubhah) that the worshippers of graves use as an analogy, which is: the existence of the grave of the Prophet (peace and blessings be upon him) in his mosque.
And the answer to that is: that the Companions (may Allah be pleased with them) did not bury him in his mosque, but rather they buried him in the house of Aisha (may Allah be pleased with her). When al-Walid ibn Abdul-Malik expanded the mosque of the Prophet (peace and blessings be upon him) at the end of the first century, he included the chamber in the mosque, and he erred in that, and some of the scholars disapproved of it, but he believed that there was no harm in it for the sake of the expansion.
So it is not permissible for a Muslim to argue with that regarding building mosques over graves, or burying in mosques; because that is contrary to the authentic hadiths; and because that is also one of the means of shirk (associating partners with Allah) with the people of the graves. And Allah is the one who grants success.