Is it permissible to sell a plot of land that was donated as an endowment (waqf) in order to contribute its price to the finishing of another nearby mosque that has been constructed?

You may dispose of the donated plot of land intended for building a mosque by selling it and building another mosque with its price or by completing an unfinished mosque, because an endowment (waqf) is not finalized until possession is taken. If possession of the plot has not been taken, then you are permitted to dispose of it. It is preferable to complete the nearby mosque if it is in need, or to build another mosque in a different area if the nearby mosque is not in need. It is not permissible to build a mosque on this plot if doing so would harm the nearby mosque.