838. To give them a mark on their right hand, or on their foreheads. That this signifies a testification of acknowledgment that they belong to the church, and are in the truths and goods, so called, of that faith, is evident from the signification of a mark, as denoting a sign or witness of acknowledgment, in this case that they belong to that church; and from the signification of the right hand, as denoting the truth of faith in its power (concerning which see above, n. 298); and from the signification of forehead, as denoting the good of love (concerning which see also above, n. 427). In this case, therefore, by the right hand and forehead are signified the truths and goods, so called, of that faith, which, nevertheless, are either not truths and goods, or falsities and evils. The acknowledgment of them, however, as being truths and goods, is signified by giving and receiving a mark upon their right hands and upon their foreheads.

A mark also signifies a sign of acknowledgment in the following passages in the Apocalypse (14:9, 11; 15:2; 16:2; 19:20; 20:4); the meaning of mark is similar to that of

"The sign" set by Jehovah upon Cain (Genesis 4:15).

Also

"The sign" which the prophet was commanded to set upon the foreheads of the men in the city of Jerusalem (Ezekiel 9:4).

As also by "the sign" in Moses:

"Thou shalt love Jehovah thy God with all thine heart, and with all thy soul, and with all thy might; thou shalt bind these words for a sign upon thine hand, and they shall be as frontlets between thine eyes" (Deuteronomy 6:5, 8; 11:18).

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.