In most cases, "mouth" in the Bible represents thought and logic, especially the kind of active, concrete thought that is connected with speech. The reason for this is pretty obvious, but it also holds when people, for instance, remove a stone from the mouth of a well, which represents gaining access to spiritual ideas. The mouth is used for eating as well as speaking, of course. In those circumstances, it represents our first, most external perception of a new spiritual idea or desire. This also makes sense, mirroring the way tasting food in the mouth gives us an instant impression of the quality of the food.

In most cases, a "master" in the Bible refers to truth. That can vary according to the person being called master -- Egyptian masters respresent factual, worldly knowledge; when the Lord is referred to as master it means Divine Truth itself. The term does vary according to context. If the things directed by the "master" represent knowledge and ideas, the master will represent desires for good, since desires for good are the things that inspire true thinking.