'Skins' or 'hides' signify external things, because the hide is the outermost organ of an animal where its interiors extend, the same as with a person's dermis or skin. 'Skin' corresponds to truth or to falsity in the extremes. See Arcana Coelestia 1835, 10036, and Apocalypse Explained 386. 'Skin,' as in Job 19:26, means the natural degree a person has with him after death.

In Exodus 22:27, this signifies things that are relatively external. (Arcana Coelestia 9215)

In Exodus 34:29, this signifies the internal of the Word shining from the external. (Arcana Coelestia 10691)

In Job 19:20, this signifies being not entirely in falsities. (Apocalypse Explained 556[11])

In Jeremiah 13:23, this signifies that evil cannot change its nature. (Apocalypse Explained 780[5])

In Genesis 3:21, this signifies that the Lord instructed them in spiritual and natural good. (Arcana Coelestia 292)

In Genesis 27:16, this signifies the external truths of domestic good. (Arcana Coelestia 3540)

6313. When a person is raised up to more internal levels he passes from the dull light on the level of the senses to a quite gentle light. At the same time he is removed from the inflow of what is disgraceful or foul and is brought closer to what is just and fair, because he is brought closer to the angels present with him, thus closer to the light of heaven. This raising up from the level of the senses was well-known to the ancients, and also to gentiles; and that is why the sages among them have said that when the mind is removed from the sensory level, it comes into inner light and at the same time into a state filled with peace and into a kind of heavenly bliss. From this they also made deductions about the immortality of the mind. A person can be raised to even more internal levels; and the further he goes, the clearer is the light that he comes into. At length he is raised up into the light of heaven, a light that is nothing else than wisdom and intelligence from the Lord. With the three heavens nothing else marks off one from another than the internal levels to which it is raised, and so also the degree of light that it possesses. Because it exists at the inmost levels the third heaven is in the greatest light, thus in wisdom far surpassing the wisdom of lower heavens.