Is placing a sum of money found on the street into a mosque's construction fund with the intention of giving charity on behalf of its owner, two days after finding it, considered charity? And if not, is it obligatory to take out the same amount and look for another charity box to place it in?

It is permissible to donate the money from a lost-and-found item (luqatah) to a mosque reconstruction fund if the amount is small, such that its owner would not pursue it. However, if it has significant value, it must be announced for a full year. If the owner is not found, the finder (multaqit) has the choice either to keep it for himself, guaranteeing it to its owner should he be identified later, or to donate it as charity.