Is it permissible to demolish an old, disused mosque and build a swimming pool in its place, using the proceeds from the swimming pool to cover the needs of a new mosque?

There is no objection to demolishing a mosque if there is a need for it and utilizing its land for the benefit of another mosque, just as Imam Ahmad permitted selling the land of a dilapidated mosque to spend on another mosque. Ibn Taymiyyah holds the view that it is permissible to replace a mosque for a greater benefit, even if it could still be used, if the benefit from the second mosque is more complete.

However, the utilization of the land must be for a good and unproblematic purpose. As for swimming pools, if they are not exclusively for children, they might involve prohibitions such as the exposure of awrahs (private parts). Therefore, it is better to utilize the land for something else. This does not mean that swimming pools free from mixing are forbidden; rather, it is a preference.