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 Genesis 9:13, this signifies the state of light in obscurity of the regenerate spiritual man. (Arcana Coelestia 1042)

In Exodus 13:21, this signifies a state of enlightenment tempered by obscurity in respect to truth. (Arcana Coelestia 81-86)

In Psalm 147:8, this signifies that the Lord defends and preserves the spiritual meanings of the Word by the natural truths in through the Bible's literal sense. (Apocalypse Explained 594[12])

In Isaiah 60:8, this signifies to search and investigate truth from the Word's literal sense. (Apocalypse Explained 282[5])

In Isaiah 19:1, the phrase 'Jehovah rides upon a light cloud, and comes into Egypt', signifies the visitation of the natural man from spiritual-natural Divine Truth, for a visitation is an examination into the quality of a man, and examination is made by means of Divine Truth. A light cloud denotes the spiritual-natural Divine Truth from which the quality of man as to his natural-self becomes evident.

(Odkazy: Apocalypse Explained 654)