The flaming sword is said to "flash back and forth" to guard the way to the Tree of Life.
This has two meanings in the form used here:
to transform oneself
to turn this way and that, turn every way
to turn this way and that, turn every way
H2015: הָפַךְ
But also, we never hear about this flaming sword again.
It's very odd.
So He drove the man out; and at the east of the Garden of Eden He stationed the cherubim and the flaming sword which turned every direction to guard the way to the tree of life.
Genesis 3:24 (NASB)