What did God mean when He said 'lest they live forever'? I was talking to a Jehovah's witness who did not believe in the immortality of soul and he pointed out a scripture to me.


  Genesis 3:22 And the LORD God said, Behold ... lest he put forth his
  hand, and take also of the tree of life, and eat, and live for ever


If the soul is already immortal what was God afraid of? Did he mean to say: 


  Lest he put forth his hand, and take also of the tree of life, and his
  soul shall stick to his body forever.


How do Protestants explain this?
One possible interpretation is that the tree of life would have given them eternal physical life.  After the Fall, this would have been in a state of separation from God.  So, God prevented them from living forever in this state of separation.

God's purpose was that they live forever in communion with Him.