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 forever: 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.
—Genesis iii, 22-24
They, looking back, all the eastern side beheld Of Paradise, so late their happy seat, Waved over by that flaming brand; the gate, With dreadful forces thronged, and fiery arms Some natural tears they dropped, but wiped them soon; The world was all before them, where to choose Their place of rest, and Providence their guide; They, hand in hand, with wandering steps and slow, Through Eden took their solitary way.
— Paradise Lost, Book XII.