That river that flowed and went out, that is, Binah that comes out of Chochmah, as said, is called the world to come as it flows constantly and never ceases. It is the Eden of the righteous that will merit life in this world to come, which is Binah that returns to Chochmah called the lower Eden (as in section 70). It constantly waters the garden, that is, the male and the female, and does not cease.
It says of it, “and like a spring of water, whose waters fail not” (Yeshayahu 58:11). This world to come was created by Yud, that is, by means of Chochmah called Yud. This is the meaning of, “And a river went out of Eden,” (Bereshit 2:10) that is, Binah that comes out of Chochmah called highest Eden; “to water the garden” (Ibid.), that is, to water the male and the female called Vav-Dalet. For fully spelled Yud comprises two letters, Vav-Dalet, that is, Yud-Vav-Dalet, as shall be explained.