'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)

4009. 'And he gave them into the hand of his sons' means that they were given to truths. This is clear from the meaning of 'sons' as truths, dealt with in 489, 491, 533, 2623, 3373. 'Giving into their hand' means giving them the right of control, for 'the hand' means power, 878, 3387. The truths which are meant by 'sons' in this case are those which are called sensory truths, for what the senses perceive as truths exist as the boundaries of the natural mind. For the natural degree of man's mind communicates on one side with sensory impressions which belong to the body and on the other side with the rational concepts which belong to the rational mind. By means of what lies in between a way of ascent so to speak is provided from sensory impressions which belong to the body, and are open in the direction of the world, up to the rational concepts which belong to the rational mind and are open in the direction of heaven. And in the same manner they provide a way of descent, that is to say, from heaven down to the world. This situation exists only with man. It is this ascent and descent that is dealt with in the internal sense of the chapters at this point in Genesis. And in order that every single thing may be expressed representatively, the rational is represented by Isaac and Rebekah, the natural by Jacob and both his wives, and the sensory awareness by the latters' sons. But since the sensory awareness as the ultimate degree of order incorporates everything prior to it each son represents something general in which those things are present, as shown above.