Q. Using haram money from Sylheti business owners abroad for funding their village Mosque restoration and repair projects?
If one uses money from unlawful earning routes to fund Mosque repairs and restoration projects or contribute towards actual parts of the Mosque, this would not be permitted because unlawful earnings cannot be given in the cause of Allah. However, Mosque toilet areas, bathroom spaces, etc. are not considered as proper parts of the Mosque and hence carry a different ruling. So, the money sourced from these expatriates can be donated for building and repairing such areas not considered to be part of the Mosque without any hope of attaining reward. Imam Ibn `Abidin states:
قال تاج الشريعة لو انفق في ذلك مالا خبيثا ومالا سببه الخبيث والطيب فيكره لأن الله تعالى لا يقبل الا الطيب فيكره تلويث بيته بما لا يقبله…
“And Taj al-Shari`a said: If he spends unlawful wealth on that or wealth acquired through both unlawful and detestable means as well as good and lawful means this would not be permitted because Allah Most High only accepts what is lawful and good. Hence, it would not be permitted to defile, tarnish or degrade his house with wealth not acceptable to Allah…”
And Allah knows best.
 See Ibn `Abidin, Radd al-Muhtar, 1:658.