I learned that they are going to sell the mosque near to me in order to buy a larger mosque. Is it permissible for them to do that?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

If someone builds a mosque and allows the people to pray in it, then it is no longer his/her property, and it becomes Waqaf (an endowment) for Allah.  It is not permissible to sell the mosque unless it becomes useless, for instance when the people of the village who live near the mosque move away from it, or that the mosque becomes too small to accommodate the people and provided it is not possible to extend it in its vicinity.  In such a case it is permissible to sell it and buy with its value another mosque.  This is the viewpoint of Hanbali school of thought.

Ibn Qudamah said in Al Mughni: 'In conclusion, if a Waqaf is destroyed or is no longer useful, like a demolished house, or devastated land, and it is not possible to build it (harvest on it), or that the people of the village move away from the mosque, and nobody prays in it, or that the mosque becomes so small and cannot accommodate the people of the village….’ Until he said: ‘….. then if the benefit of the Waqaf is not totally stopped but was only minimized, and the benefit is in a different and bigger place, it (the mosque) has to be given back to the Waqaf, and it is not permissible to sell it, because selling it is forbidden in principle.  However, it is permissible to sell it in the case of necessity, to preserve the Waqaf from being lost when it is possible to still benefit from it – even if the benefit is minimized – unless the benefit is no longer considered as such or is not beneficial at all; so it is considered as inexistent or similar to the inexistent’. The text of Ibn Qudamah ends here.

However, Abu Hanifa, Malik and Shafi’e are of the viewpoint that it is not permissible to sell the mosque at all.

Nevertheless, Ibn Taymiyah, may Allah have mercy on him, gave a Fatwa that it is permissible to exchange the mosque with another one for more benefit, even if it is possible to benefit from the first mosque.  So, it is unlawful to sell this mosque unless it has become too small for Muslims to pray in and provided it cannot be expanded in its own vicinity.

Allah knows best.