How can the benefit of a waqf land be preserved, given that it is surrounded by neighbors' fences on three sides, leaving no access to it except through the grandfather's land, which the heirs wish to sell? Can this waqf land be sold to purchase another, or to build a mosque with its proceeds?

The question should be referred to the Sharia Court or the responsible authorities to investigate the establishment of the endowment (waqf), the possibility of utilizing it, and the ruling on selling and replacing it, because the ruler's judgment resolves disputes. The preponderant opinion is that it is permissible to sell an endowment to purchase another one if it is more beneficial and closer to realizing the endowment's interest, and this is the view chosen by Ibn Taymiyyah.