Genesis 3:24

And He drave out the man from thence where He had made to dwell the glory of His Shekina at the first between the two Kerubaia. Before He had created the world, He created the law; He prepared the garden of Eden for the righteous, that they might eat and delight themselves with the fruit of the tree; because they would have practised in their lives the doctrine of the law in this world, and have maintained the commandments: (but) he prepared Gehinnam for the wicked, which is like the sharp, consuming sword of two edges; in the midst of it He hath prepared flakes of fire and burning coals for the judgment of the wicked who rebelled in their life against the doctrine of the law. To serve the law is better than (to eat of) the fruit of the tree of life, (the law) which the Word of the Lord prepared, that man in keeping it might continue, and walk in the paths of the way of life in the world to come.

ויגרש את האדם, in order to ensure that neither he nor his offspring would return to Gan Eden.

וישכן, G’d placed the cherubs there simultaneously with Adam’s departure.

לשמור את דרך עץ החיים, to ensure that on the way out they would not take from its fruit and eat thereof.

ויגרש את האדם, this is not a repetition, but the Torah explained that simultaneously with Adam’s expulsion from the garden G’d had placed the cherubs there as guardians מקדם, in the East. It is possible that the entrance of the garden was in the east, and that is why the cherubs were placed at the entrance. They were beings who appeared to the onlooker just like cherubs, in order to put fear into Adam, to discourage him from attempting to return to Gan Eden, this is why it continues with the words לשמור את דרך עץ החיים ואת להט החרב המתהפכת, the revolving sword blades held by the cherubs were meant to frighten Adam. Seeing that the sword was not real, but only appeared so to Adam, the Torah speaks of the להט החרב, “the blade of the sword,” and not the sword itself. The word להט does not describe something of substance but something imaginary, flashes of the spectacle being what is frightening to behold. When this “fire, flame” keeps revolving around itself, as described here, this increases the fear inspired in the person watching such a spectacle. In Ezekiel 32,10 we have a similar expression עופפי חרבי, when G’d is described as frightening people by “brandishing My sword.”
There is an additional element in this, i.e. the spectacle is meant to inspire feelings of remorse over what he had done in Adam. Once Adam felt remorse, the way would be paved to full repentance. Once he had done תשובה the frightening spectacle would disappear and he would return to the garden from time to time, alternating between performing work there and working the soil outside. (one opinion in Bereshit Rabbah 21,8) All these matters have also been discussed in their mystical dimension in the writings of the Kabbalists. In Bereshit Rabbah 21,9 the word להט is understood as applying to certain angels, as mentioned in Psalms 104,4 עושה מלאכיו רוחות, משרתיו אש לוהט, “He makes the winds His messengers, fiery flames His servants.”
המתהפכת, a reference to G’d’s servants revolving, be they mane, women, or spiritual, disembodied beings such as winds, or even angels.

להט, “flaming;” ,the expression “flaming sword,” is a metaphor describing hell which is presumed as a domain in which freezing cold and burning heat constantly alternately, inflicting indescribable discomfort on its wicked inhabitants.