What is the ruling on prayer if there is a grave in the middle of the mosque?

Question:
What is the ruling on prayer if there is a grave present in the middle of the mosque?

Answer:
The prayer is valid. The Messenger of Allah (peace and blessings be upon him) said:
Unless the grave is the original one and the mosque was built over it, in which case the mosque must be demolished. It is the duty of the Islamic state to demolish the mosque.
As for if the grave is the new one and the mosque is old, it is obligatory to dig up the grave and move it to another location.
Q: Is there an exception in this case regarding the grave of the Prophet (peace and blessings be upon him)?
A: No, it is where it is in the mosque. This is in the house of 'A'ishah. The mistake was when al-Walid brought it into the mosque when they expanded the mosque; it became a source of doubt for those with weak insight. The blame is on the one who brought it in.
Q: One who prayed in a mosque that has a graveyard and did not know, does he repeat the prayer?
A: He repeats it, yes.
Q: I have been praying for how many years, I do not know about it?
A: You repeat it.
Q: I do not know how many prayers?
A: According to your estimate.
Q: What is the order?
A: The order is each day for itself, according to your estimate.