God placed cherubim and a flaming sword

2. Alma 12: 21
     21 What does the scripture mean, which saith that God placed cherubim and a flaming sword on the east of the garden of Eden, lest our first parents should enter and partake of the fruit of the tree of life, and live forever? And thus we see that there was no possible chance that they should live forever.
3. Alma 42: 2-3
     2 Now behold, my son, I will explain this thing unto thee. For behold, after the Lord God sent our first parents forth from the garden of Eden, to till the ground, from whence they were taken—yea, he drew out the man, and he placed at the east end of the garden of Eden, cherubim, and a flaming sword which turned every way, to keep the tree of life—
     3 Now, we see that the man had become as God, knowing good and evil; and lest he should put forth his hand, and take also of the tree of life, and eat and live forever, the Lord God placed cherubim and the flaming sword, that he should not partake of the fruit—