The basis for this question stems from Genesis 2:17.
Genesis 2:17
“but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall surely die.”
Some have claimed that the Bible doesn’t necessarily mean what it says in Genesis 2:17, since Adam and Eve didn’t die the moment they ate. They argue that the passage really means “die,” not “surely die,” which is what gives the implication that Adam and Eve will die on the same day they eat.
It is true that Adam and Eve didn’t die the exact day they ate (Genesis 5:4–5) as some seem to think Genesis 2:17 implies. So, either God was in error or man’s interpretation is in error. Since God cannot lie (Hebrews 6:18), then fallible humans must be making the mistake.
Let’s take a look at where the confusion arises. The Hebrew phrase in English is more literally:
“Tree knowledge good evil eat day eat die (dying) die”
The Hebrew is, literally, die-die (muwth-muwth) with two different verb tenses (dying and die), which can be translated as “surely die” or “dying you shall die.” This indicates the beginning of dying, an ingressive sense, which finally culminates with death.
At that point, Adam and Eve began to die and would return to dust (Genesis 3:19). If they were meant to die right then, the text should have simply used muwth only once, which means “dead, died, or die” and not beginning to die or surely die (as muwth-muwth is used in Hebrew). Old Testament authors understood this and used it in such a fashion, but we must remember that English translations can miss some of the nuance.
There are primarily two ways people translate: one is literal or word for word (formal equivalence) and the other is dynamic equivalence or thought-for-thought. If this is translated word for word, it would be “dying die” or “die die,” which is difficult for English readers to understand, as there is no changed emphasis when a word is repeated. The Latin Vulgate by Jerome, which permits such grammatical constructions, does translate this as “dying die” or “dying you will die” (morte morieris). So, most translations rightly use more dynamic equivalence and say “surely die.”
With regards to the Hebrew word yom for day in Genesis 2:17, it refers specifically to the action of eating and not “dying die.” Solomon used an almost identical construction in 1 Kings when referring to Shimei:
1 Kings 2:37
“For on the day <yom> you go out and cross over the brook Kidron, you will know for certain that you shall surely <muwth> die <muwth>; your blood shall be on your own head.”
This verse uses yom (day) and the dual muwth just as Genesis 2:17 did. In Genesis 2:17, yom referred to the action (eating) in the same way that yom refers to the action here (go out and cross over). In neither case do they mean that was the particular day that death would come, but the particular day they did what they weren’t supposed to do.
Solomon also understood that it would not be a death on that particular day but that Shemei’s days were numbered from that point. In other words, their (Adam and Shimei) actions on that day were what gave them the final death sentence—they would surely die as a result of their actions. Therefore, the day, in Genesis 2:17 was referring to when Adam and the woman ate, not the day they died.
Some people believe that the punishment was not really death, but that sleep (not deep sleep) entered the world at this time. Although this is not meant to be an exhaustive examination, I would lean against sleep being the punishment referred to in Genesis 2:17, since many other passages in the Bible describe sleep as a good thing. For example, sleep is pleasant in Ecclesiastes 5:12 and Jeremiah 31:26. The Lord often appeared to people while they were sleeping, and He Himself slept during a storm (Matthew 8:24; Mark 4:38; Luke 8:23). Also, Solomon’s pronouncement against Shimei would not make any sense, as there is no doubt that Shimei already slept on a regular basis.
What is spoken of in Genesis 2:17 is a punishment and the foundation for Christ’s physical death. If He merely had to sleep, then this undermines the reason for Christ’s work on the cross. Recall Romans 5:12: His death was a real death.
From a quick search, there are few passages referring to sleep as death in the Old Testament, such as Daniel 12:2 and Psalm 90:5, where much imagery is given in the context and so leads us to realize the metaphorical nature of the passages. For example in the following verse in Daniel, those with insight will shine brightly. Obviously, it is not referring to a literal physical light emanating from humans. In the same figurative manner, people are compared to grass in Psalm 90:5.
The New Testament, written in Greek, does this as well. Jesus figuratively said that Lazarus was sleeping in John 11:11–13. The disciples failed to understand and took it as literal sleep, so Jesus had to correct them (John 11:14).
Regardless, this punishment was a real death, and Adam and Eve died—as will all the rest of us for our sins, which is all the more reason to receive Christ and be saved from death so that death will no longer have a sting (1 Corinthians 15:53–57).
http://www.answersingenesis.org/articles/2010/03/09/satan-the-fall-good-evil-why-didnt-adam-die-instantly