Is an employee entitled to keep an erroneous raise that reached his salary, and is he permitted to dispose of it or give it as charity?

The error that occurred in transferring money to the man's account does not make it permissible for him to take it or dispose of it. Nor is it permissible for him to give it as charity while knowing its owner. Rather, he is obliged to return it in full. If he disposes of it, he guarantees it, and it becomes a debt upon him, and its owner has the right to demand it in full or in installments.