What is the Biblical basis for the belief that separation from God is in itself sin? The normal understanding in Christianity is that sin brings separation from God. However is there biblical basis for holding to the belief that separation from God is in itself sin rather than a consequence of sin?
I can think of one clear-cut verse off the top of my head. Assuming that the question you are asking is about one who was once not separated from God but later became separated (actually this is true for all man if you think about it, since man was with God at the beginning and later separated himself from God)


  Jer. 2:13  For My people have committed two evils: / They have
  forsaken Me, / The fountain of living waters, / To hew out for
  themselves cisterns, / Broken cisterns, / Which hold no water.


Of course, you can also read into the context of the Bible and see. When man decided to eat of the tree of knowledge of good and evil rather than the tree of life, he actively made a choice to choose the representative of Satan (tree of knowledge) over God (the tree of life). In this way, the original sin itself is actually the act of separating himself from God in the way of disobedience.