What is the ruling of Islamic law regarding building a school on land endowed for a mosque (waqf al-masjid) and using part of it as a football field without paying rent for it?

Land endowed for a mosque may not be utilized except with the permission of its trustee. The trustee may not dispose of it except in a way that benefits the endowment. Therefore, it is not permissible to give it to someone who exploits it without rent. Rather, rent must be collected from anyone who benefits from it and spent on the mosque's welfare. The same ruling applies to the plot designated for playing football, with the obligation to avoid anything that disturbs worshippers or contradicts Islamic morals.