To dream of a prison guard represents you or someone else that is concerned that a restriction holds. Feeling that repaying debts or suffering punishment is mandatory. Feeling that nobody will help you escape the consequences of your actions. It may also reflect a person or situation that is making sure you face your karma whether you like it or not.
Alternatively, a prison guard may represent acceptance of your own guilt. A part of you that knows your guilty and must do something about it. Punishing yourself or feeling that the consequences must be repaid. Restricting your own growth or happiness.
To dream that you are a prison guard represents your wish to restrict someone else or make sure they face the consequences of their actions. It may also reflect your attempt to make sure that debts are repaid or the punishment is experienced in full. Not letting someone off easy.
Example: A man dreamed of being handed a white bible by a prison guard. In waking life he was actually in prison and felt that he had to change his ways because he knew he was guilty.