Why does Scripture in parashat bereishit need to mention the four rivers?

Question

In Bereishit 2:10, scripture mentions the following:

10: And a river flowed out of Eden to water the garden, and from there it separated and became four heads.

11: The name of one is Pishon; that is the one that encompasses all the land of Havilah, where there is gold.

12: And the gold of that land is good; there is the crystal and the onyx stone.

13: And the name of the second river is Gihon; that is the one that encompasses all the land of Cush.

14: And the name of the third river is Tigris; that is the one that flows to the east of Assyria, and the fourth river that is the Euphrates.

It doesn't seem to be really adding anything useful--and completely out of context--to the previous topic, and the following topic. Why do we need to know about the four rivers?

Answer 1

The Malbim in his commentary to Bereishis 2:10 and following pesukim seems to adress this question. He says that history has proven that mankind tended to dwell on riverbanks (hence the account of Adam when cast out of Eden would fit later). And also the description of the rivers would indicate that God prepared good conditions for Man to disperse over various places each one of them different and influencing its people accordingly. The description of the four rivers allegorize this by saying some traits that mankind would be divided:

1) Pishon represents the ones who strive after enrichment and treasures under the sky. The posuk 11 exempifies this by mentioning the land of Havilah, "where there is gold".

2) Guihón, alludes to the ones who strive after the satisfaction of sexual desire, that's why Ezekiel 23:20 describes the inhabitants of the land of Kush as the ones "whose phallus were like those of donkeys".

3) Tigris (Hidékel) represent the ones who strive after power and provoke war. The Kings of Ashur are exemples of that.

4) and the last one, the Euphrates (connected to eretz yisroel, Shevuot 47b) represents the uniqunesse of those who raise great sages.

Answer 2

1) I heard the following explanation (which may be the Waters of Eden referenced above):

Impurity comes from death. Death is a post-Garden of Eden reality. The waters of the world are sourced back to the Garden of Eden. Therefore immersing in them accomplishes returning one's self to the Garden of Eden, where there is no such thing as death. Therefore, a mikvah has the ability to remove impurity (which comes from death) because it is water from the Garden of Eden.

It is important to know that it is part of the geography of Gan Eden, and that it departs from there. The reason water has the quality that it has is because it comes from Gan Eden. Additionally, this is the only place that discusses the layout of Gan Eden, so it belongs specifically here.

2) In the book (novel) With All My Heart With All My Soul by (pseudonym) B.D. Daehu, he says an explanation that I don't fully appreciate. He explains an approach very similar to that of Lonely Man of Faith about the two accounts of creation of Adam, and concludes with a comment about the rivers being in the second section as the calm, quiet flow of the rivers speaks to the solitary state of man, which is the theme of the second account of Man's creation in his approach.