If there is a grave in the mosque, then if someone says, from the standpoint of safety: let us make a door for the mosque and a door for the grave to separate them

The questioner : May Allah reward you. As for the grave in the mosque, if someone says that from the standpoint of safety, one should put a door for the grave and a door for the mosque so that the grave is separated from the mosque, does this statement have a valid point?

The Shaykh : Is it?

The questioner : Does this statement have a valid point?

The Shaykh : No. It is said that if the mosque is built over the grave, it must be demolished, and prayer in it is not permissible, because building it is a sin against Allah and His Messenger.
As for if the mosque was built first and then the deceased was buried in it, if it is in the direction of the qiblah, prayer toward it is forbidden. If it is behind the qiblah, or to its right, or to its left, then prayer in the mosque is permissible. However, it is obligatory for the family of the deceased and the authorities in the town to dig up this grave and bury it with the people, because the mosque is not permissible to be used for anything other than prayer. Do you understand?

The questioner : Yes

The Shaykh : Yes.