In Genesis 49:12, "teeth whiter than milk" signify the Celestial Spiritual [milk] in the Lord's Natural [teeth], where Judah is here representing the Lord. (Arcana Coelestia 2184-2185).

In Psalms 3:7; 37:12, 58:6; Matthew 8:12, teeth signify the lowest natural things in man: in the genuine sense, their truths, in the opposite sense, their falsities. So the gnashing of teeth signifies the collision of falsities with truths. (Arcana Coelestia 4424[3])

In Exodus 21:27, this signifies truth in the natural, here the ultimate, which is the sensuous. (Arcana Coelestia 9062)

The tooth signifies the corporeal proprium, which is the lowest degree of man. (Arcana Coelestia 10283[12])

'Teeth,' as in Genesis 49:12, in the genuine sense, signify the natural level of life. Any hard part of the body, like bones and cartilage, corresponds to the truths and goods of the lowest natural level. 'Teeth' signify the outer edges of the life of the natural self, or the sensory level. There is a natural sensory will, and a natural sensory understanding. When the sensory levels are separated from the interior of the mind, their supposed truths are really mere falsities, and do violence to truths and destroy them. This situation appears in many passages, because sensory people do not see any truth in its own light, but engage in reasoning and altercations about everything... These altercations are heard in the hells as the gnashing of teeth. Viewed in itself, this is the collision of falsity and truth. This is the meaning of 'gnashing of teeth' in Matthew 8:12, 13:42, 50, 22:13, 24:51, 25:30, and Luke 13:28.

(References: Apocalypse Revealed 435)

1577. That 'let there not be strife, now, between me and you, [and between my herdsmen and your herdsmen]' means that there ought to be no disagreement between the two becomes clear from what has been stated already. This agreement, or unity, of the internal man and the external man contains more arcana than can ever be fully told. The internal man and the external man have never been united in anyone - for it never has been possible nor is it ever possible for them to be united - except in the Lord; and this is a further reason why He came into the world. With people who are regenerate the internal man and the external man appear as though they are united; but in fact they are the Lord's, for the things that are in agreement are the Lord's, whereas those that are not are man's.

[2] There are two sides to the internal man, namely the celestial and the spiritual, and these two form a single entity if the spiritual has its origin in the celestial. Or what amounts to the same, there are the two sides to the internal man known as good and truth. These two form a single entity if truth has its origin in good. Or what also amounts to the same, there are the two sides to the internal man, love and faith. These two form a single entity if faith has its origin in love. Or what yet again amounts to the same, there are the two sides to the internal man, will and understanding. These two form a single entity if the understanding has its origin in the will. The light from the sun can serve to make the point plainer still. If both warmth and light are present in light from the sun, as they are in spring-time, all things consequently start to grow and thrive. But if, as in winter, there is no warmth in the light from the sun all things at that time consequently fade and die.

[3] From this it is clear what constitutes the internal man. What constitutes the external man however is evident from the fact that with the external man everything is natural; for the external man is one and the same as the natural man. The internal man is said to be united to the external when the celestial-spiritual comprising the internal man flows into the natural comprising the external man and causes them to act as one. The natural as a consequence becomes celestial and spiritual as well, though it is a lower variety of celestial and spiritual. Or what amounts to the same, the external man as a consequence becomes celestial and spiritual as well, though it is a more exterior variety of celestial and spiritual man.

[4] The internal man and the external man are completely distinct and separate since celestial and spiritual things are what move the internal man but natural things the external man. But although they are distinct they are nevertheless united, that is to say, when the celestial-spiritual comprising the internal man flows into the natural comprising the external man and reorganizes it as its own. In none but the Lord has the Internal Man been united to the external Man. It has happened to nobody else except insofar as the Lord has united and does unite them. It is solely love and charity, that is, good, which effects union, and there can never be any love and charity, that is, any good, unless it comes from the Lord. Such is the union which these words of Abram are meant to convey - 'let there not be strife, now, between me and you, and between my herdsmen and your herdsmen, for we are men who are brothers'.

[5] The words 'between me and you, and between my herdsmen and your herdsmen' are used for the following reason: just as the internal man has two elements, namely the celestial and the spiritual which, as has been stated, form a single entity, so too does the external man. The celestial side of the external man is called natural good, the spiritual side natural truth. 'Let there not be strife between me and you' has regard to good - that is, let there be no conflict between good in the internal man and good in the external, while 'let there be no strife between my herdsmen and your herdsmen' has regard to truth - that is, let there be no conflict between truth in the internal man and truth in the external.