What is the ruling on praying in a mosque built on land that some elders claim is an endowment (waqf) for another mosque, without any documents to prove it, while the seller possesses official documents, knowing that the mosque is built upon the Sunnah and serves the people of the village? And what is the opinion regarding those who warn people against praying in it?

Prayer in the mosque is valid, and no attention should be paid to the unsubstantiated words of the elders. The documents held by the seller prove the validity of the land ownership. Continue praying and do not pay attention to words without legitimate evidence. Whoever warns against praying in it must provide evidence; otherwise, it is not permissible for him to do so. An endowment (waqf) may not be sold, but if the mosque for which it was endowed does not need the land, then it is permissible to offer it to someone who will build a mosque upon it.