What is the ruling on the surplus money from donations for building a mosque?

The questioner : How do we understand the critics, when the Prophet (peace and blessings be upon him), on one occasion, said: I had a sum of money specifically for a mosque in a village.

The Shaykh : And where, brother?

The questioner : Specifically for a mosque in a village. I had a sum of money specifically for a mosque in a village, and the mosque is complete with all its buildings. Then I found that I could pay the amount to the brothers in i'tikaf (spiritual retreat in the mosque), regarding da'wah (calling others to Islam) and Islamic work, as well as regarding the repair and whitewashing of the mosque. What is your opinion on this, and did I do right or wrong?

The Shaykh : If people donate to build a specific mosque and its construction is finished with some money remaining, what do we do with this surplus? The answer is: if the donors are known by name, meaning if the donors are identified and known, it is obligatory for him to inform them and say that a surplus of money remains. Then they choose what they wish to do with it. If the donors are not known, and a surplus remains from this money, it is obligatory that it be spent on the same type of thing for which it was donated. What was it donated for? Building mosques. So the surplus is paid toward building other mosques. It is not given to those in i'tikaf, because i'tikaf is a different category from building mosques. This answer is the answer to the questioner's question. We tell him: this surplus, if the donors are known, seek their permission and inform them of the surplus. If they are not known, spend it on building another mosque.