It is not permissible to dispose of wealth given as a waqf for the mosque by lending or borrowing
Question

                What is the ruling on borrowing or lending to someone money that belongs to the mosque, that was collected to spend on what the mosque needs?.
Praise be to Allah.
    Money that is collected to be spent on the mosques and what 
    they need is money that is part of a waqf and it is not permissible for the 
    one who is in charge of it to borrow any of it for himself or to lend any of 
    it to anyone. He is entrusted with this money to spend it in the manner 
    dictated by those who donated it, which in this case is what the mosque 
    needs, and it is not permissible to dispose of it in any other way. 

    Shaykh Zakariya al-Ansaari (may Allah have mercy on him) 
    said: 

    The one who is in charge of it has no right to take anything 
    from the property that has been given as a waqf on the basis of liability, 
    and if he does that then he is liable. … and it is not permissible for him 
    to lend it, i.e., the waqf property. This is like lending the wealth of a 
    child under one’s care. End quote. 

    Asna al-Mataalib fi Sharh Rawd al-Taalib, 
    2/472 

    Shaykh Mansoor al-Bahooti (may Allah have mercy on him) 
    said: 

    The one who lends an item to another should have the 
    authority to donate it. Therefore the guardian of an orphan cannot lend the 
    orphan’s property to anyone; the same applies to one who is entrusted with a 
    waqf. 

    End quote. Sharh Muntaha al-Iraadaat, 2/100 

    i.e., it is stipulated in the case of lending that the lender 
    should should have the authority to donate what he is lending. Therefore it 
    is not permissible for an orphan’s guardian to lend from the orphan’s 
    property, and it is not permissible for the person in charge of a waqf to 
    lend from the waqf property, because he has no authority to do so. 

    And Allah knows best.