A river flowed out of Eden to water the garden, and there it divided and became four rivers.
10. And a river went out Moses says that one river flowed to water the garden, which afterwards would divide itself into four heads. It is sufficiently agreed among all, that two of these heads are the Euphrates and the Tigris; for no one disputes that הידקל( Hiddekel ) is the Tigris. But there is a great controversy respecting the other two.
Man consisting of body and soul, a body made out of the earth and a rational immortal soul the breath of heaven, we have, in these verses, the provision that was made for the happiness of both; he that made him took care to make him happy, if he could but have kept himself so and known when he was well off.
Commenting on Genesis 2:8-15
And a river went out of Eden to water the garden,.... Before man was created, as Aben Ezra observes, this river went out of Eden and watered it on every side; but what river is here meant, is hard to say.