Is exchanging foreign currency for hotel guests into Qatari Riyals considered permissible (halal) or impermissible (haram) personal wealth?

The basic principle is the permissibility of trading currencies and profiting from the differences in their exchange rates, provided that the Sharia (definition)-compliant rules of currency exchange are observed. The most important of these is the occurrence of qabd (possession/handing over) in the contract session, based on the Prophet's (peace be upon him) saying: "If these types [of commodities] differ, then sell as you wish, provided it is hand-to-hand." However, the employer's permission is necessary because the employee's benefit is owned by the employer, as the employee is a private ajeer (hired person).