when the monkey found that he was being crushed under the mountain he was greatly distressed.

he cried out, "oh, master you delivered me from under the mountain before, and trained me in religion;  how is it that you've brought me into this pass?

if we all must die - why must everyone suffer?

 

his tears poured down like the rain from above.

 

the mountains are a part of the earth that reaches into the heavens, so they've come to be a symbol that unifies heaven and earth.