Is taking a waqf Qur'an designated for the mosque, from a person who wants to place it there, for personal use, considered an encroachment upon the mosque's waqf?

If a person dedicates a Qur'an as an irrevocable endowment (waqf) for the sake of Allah Almighty, it has left his possession and may not be diverted to another entity. However, if he intended to dedicate it but did not formalize the endowment, or if he formalized it without specifying the beneficiary, then it is permissible to dedicate it to another entity. Accordingly, if the man dedicated the Qur'an as an irrevocable endowment, it must remain as he specified; otherwise, there is no sin in what you both have done.