What is the ruling on lending Qurans for Tahajjud prayer in the mosque to someone who needs a large-print Quran, knowing that they are not being used and are gathering dust?

It is not permissible to take the Mus'haf out of the mosque for someone who wants to read from it if the Mus'hafs are endowed for the mosque; because that entails appropriating something that is common to all Muslims, and a violation of the endower's condition.