Is it permissible for a Muslim to establish and manage a shop on land that belongs to the mosque's endowments?

It is not permissible to exploit land endowed for a mosque (waqf land), whether it is part of the prayer hall or its annexes, for building private shops, as this is an encroachment on the right of Allah and the Muslims. However, if the land was endowed for exploitation and spending on the mosque, it is permissible to build shops on it, provided that they are not owned by a specific individual, and their income remains for spending on the mosque or other charitable endeavors according to the condition of the endower. Sheikh Ibn Baz affirmed that the mosque's land and its courtyards remain an open space for the mosque to be used for prayer when needed, and it is not permissible to build on them for a private purpose; rather, private buildings for the imam or the library should be outside the mosque.