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

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.