What is the ruling of Sharia on a man who rented a shop belonging to the mosque and then sold it after a period of time?

If the intent is that the man rented the mosque's premises and sold his goods and then left, there is no harm in that. However, if he sold the commercial property owned by the mosque, it is not permissible. He must repent, annul the sale, return the price, and keep the property as belonging to the mosque.