Alma 12:23

And now behold, I say unto you, that if it had been possible for Adam for to have partaken of the fruit of the tree of life at that time, that there would have been no death, and the word would have been void, making God a liar: for he said, If thou eat, thou shalt surely die.—

If Adam could have eaten from the tree of life after that, no one would die. That would make God’s word wrong. It would make God a liar. He said: If you eat it, you will die.

If Adam had been able to eat from the tree of life after his sin, there would have been no death. God’s word would have been meaningless—it would have made him a liar. Because he said, ‘If you eat, you will surely die.’