And the LORD God said, Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever:
Therefore the LORD God sent him forth from the garden of Eden, to till the ground from whence he was taken.
So he drove out the man; and he placed at the east of the garden of Eden Cherubims, and a flaming sword which turned every way, to keep the way of the tree of life.
http://biblehub.com/genesis/3-22.htm