In what way is "nature" comparable to heaven in Of Mice and Men?

Several characters in this multi-layered story have ideas about what Heaven would be to them.  George's ideas of Heaven are always closely tied to freedom.  Steinbeck links George and his dreams of freedom to the little camp he and Lennie make in the first chapter:

"Tomorra we're gonna go to work. I seen thrashin' machines on the way down. That means we'll be bucking grain bags, bustin' a gut. Tonight I'm gonna lay right here and look up. I like it."

George loves lying under the stars and having no one to answer to, out in the open air.  George and Lennie have visions of their own "Heaven" in the form of a little idyllic farm, where they will be free from the prying eyes of others and the dangers of Lennie's misbehavior.  Steinbeck uses nature imagery to describe the farm:

"An' live off the fatta the lan'," Lennie shouted. "An' have rabbits. Go on, George! Tell about what we're gonna have in the garden and about the rabbits in the cages and about the rain in the winter and the stove, and how thick the cream is on the milk like you can hardly cut it. Tell about that George."

Crooks sees "land" as the equivalent of "Heaven" in this negative view of George and Lennie's prospects for ever being able to attain their version of Heaven:

"I seen hunderds of men come by on the road an’ on the ranches, with their bindles on their back an’ that same damn thing in their heads. Hunderds of them. They come, an’ they quit an’ go on; an’ every damn one of ‘em’s got a little piece of land in his head. An’ never a God damn one of ‘em ever gets it. Just like heaven. Ever’body wants a little piece of lan’. I read plenty of books out here. Nobody never gets to heaven, and nobody gets no land.

The most prominent place where Steinbeck links nature to Heaven comes in the last chapter.  When George is telling Lennie about the "little place" one last time, he tells Lennie to look across the river, knowing he is about to end Lennie's life.  In the Bible on two different occasions, the Jews are led across a body of water on dry land to escape their enemies.  This idea of "crossing the river" has become to symbolize crossing over into a new life for Christians.  The natural water imagery depicted in Lennie's final scene, combined with his traditional ideas of his version of Heaven on Earth (the little farm), work together to give the reader assurance of Lennie's transition to a better life after death.