2 Nephi 2:18

And because that he had fallen from Heaven, and had become miserable forever, he sought also the misery of all mankind.—Wherefore, he sayeth unto Eve, yea, even that old serpent, which is the Devil, which is the father of all lies; wherefore he sayeth, Partake of the forbidden fruit, and ye shall not die, but ye shall be as God, knowing good and evil.

Because he fell from heaven, he became sad forever. So he wanted all people to be sad too. He is that old snake, the Devil, the father of all lies. He said to Eve: Eat the forbidden fruit. You will not die. You will be like God, knowing good and evil.

Because he fell from heaven and became miserable forever, he wanted everyone else to be miserable too. That old serpent—the devil, the father of all lies—said to Eve: “Eat the forbidden fruit. You won’t die. You’ll be like God, knowing good and evil.”