What is the ruling on some bookstores selling religious books on condition of purchasing other books at a certain minimum to obtain free waqf books, and refusing to give them for free to those who do not purchase?

Whoever takes endowed books must distribute them according to the conditions of the endower, for the endower's condition is to be considered as long as it does not contravene Islamic law. It is not permissible for the library to compel anyone to purchase books from the library in exchange for receiving the endowed books if the endowment entity did not stipulate that, as this is a stratagem to gain compensation for the endowment, and an endowment may not be sold. This is based on the Prophet's (peace be upon him) statement to Umar ibn al-Khattab (may Allah be pleased with him): "Donate its essence, it is not to be sold, nor given away, nor inherited, but its fruits are to be spent." What is distributed free of charge is considered an endowment and may not be sold or traded. It must be given to those who need it when one no longer needs it. Those in charge of libraries should be advised to distribute the books as the endowing entity intended.