Should the mosque be sold or demolished when the inhabitants leave?
Question

                We have a mosque in our location where we say our regular prayer including JUMMA prayer. Now we are leaving the complex and this complex is going to be handed over to another people who are non-muslims. Basically it is their complex. We have been here for our temporary duty for six years. Now after comletion of our duty we leaving it to them. So. what to do with the mosque? Should we break it down or keep it as it? As they are non-muslims، none is going to say prayer there unless Allah wishes otherwise. Again if we leave it as it is there is scope of misuse. Please advise us what to do with the mosque?.
Praise be to Allah.
    If the waqf is no longer of benefit and it is not possible to 
    benefit from it, it is permissible to sell it according to the correct 
    scholarly opinion, whether it is a mosque or anything else. If the people of 
    the mosque are moving to another place and there will no longer be any one 
    who could benefit from it, it is permissible to sell it and use the money to 
    build another mosque. 

    Ibn Qudaamah may Allah have mercy on him) said: If a waqf 
    falls into disrepair and is no longer of any benefit, such as if a house 
    collapses and it is not possible to rebuild it, or the people of the village 
    move away from a mosque so people no longer pray in the mosque, or it has 
    become too small for the congregation and it is not possible to expand it 
    where it is, or if its walls have developed cracks and it is not possible to 
    repair them or part of them except by selling part of it, then it is 
    permissible to sell part of it in order to repair the rest of it. 

    If it is not possible to benefit from any part of it, it is 
    permissible to sell the whole of it. 

    Imam Ahmad said: If there are two wooden beams in the mosque 
    that are of value, it is permissible to sell them and spend the money on the 
    mosque. 

    He also said: A mosque may be moved if there is the fear of 
    thieves, if its location is dirty? Al-Qaadi said: i.e., if that is keeping 
    people from praying in it.

    End quote from al-Mughni, 5/368. 

    Shaykh Ibn Baaz (may Allah have mercy on him) said:

    If the waqf is no longer of benefit, whether it is a mosque 
    or otherwise, it is permissible to sell it according to the more correct of 
    the two scholarly opinions, and its price may be spent on another waqf of 
    equal value to replace the first waqf if possible. It was narrated from 
    Ameer al-Mu’mineen ‘Umar ibn al-Khattaab (may Allah be pleased with him) 
    that he issued instructions that the mosque of Kufah be moved to another 
    location because there was an interest that could be served by doing so. 
    Therefore when a mosque is no longer of any benefit at all, it is more 
    appropriate to suggest that it is permissible to move it. However, this is a 
    matter concerning which there is a difference of opinion among the scholars, 
    but the reliable view is that it is permissible because Islamic sharee‘ah is 
    perfect and came to achieve and fulfil what is in people’s best interests 
    and to cancel and reduce that which is detrimental to their interests; it 
    enjoins preserving wealth and forbids neglecting or wasting it. There is no 
    doubt that if a waqf is no longer effective there is no interest to be 
    served by keeping it; rather keeping it is a waste of money. So it should be 
    sold and the money spent on something similar.

    End quote from Fataawa ash-Shaykh Ibn Baaz, 20/11 

    If this mosque can be sold to someone who will use it for 
    something permissible, such as a hospital for example, after removing its 
    minaret and changing its appearance, it is permissible to sell it as it is, 
    without demolishing it, because of the interest that will be served which is 
    to bring a higher price than if (the land) were to be sold after demolishing 
    it. 

    If there is the fear that it will be used for some haraam 
    purpose, then it is to be demolished and the land sold, and the money should 
    be spent on another mosque. 

    And Allah knows best.