What is the ruling on selling in the basement of the mosque designated for memorizing the Qur’an, and does that fall under the ruling on selling in the mosque, and what is incumbent upon one who has sold there?

The fundamental principle is that everything connected to the mosque and falling within its perimeter, such as rooms, basements, and courtyards, takes the ruling of the mosque. Therefore, buying, selling, and advertising are prohibited therein, based on the Prophet's (peace be upon him) saying: "If you see someone buying or selling in the mosque, say: 'May Allah not make your trade profitable.'"

Two exceptions apply: 1. If the intention of the endower was that the basement or room does not belong to the mosque, then it does not take its ruling, and buying and selling are permissible therein. 2. If the rooms are outside the mosque's perimeter, even if their doors open into it.

As for someone who sold before knowing the religious ruling, their sale is valid, based on the Almighty's saying: ﴿So whoever receives an admonition from his Lord and desists, he may have what has already passed, and his affair is left to Allah. But whoever returns [to wrongdoing] - those are the companions of the Fire; they will abide therein eternally﴾. However, she must refrain from such actions in the future.