How did the livestock of the Egyptians die twice? Yesterday we were studying the ten plagues in Exodus. One of the things that confused us was this. Exodus 9:6 reads: 


  6 And the next day the Lord did it: All the livestock of the Egyptians died, but not one animal belonging to the Israelites died. [NIV]


This means, the Egyptians did not have any livestock left. But in verses 20 and 21 we read:


  20 Those officials of Pharaoh who feared the word of the Lord hurried to bring their slaves and their livestock inside. 21 But those who ignored the word of the Lord left their slaves and livestock in the field.


Wait, which livestock? Wasn't the livestock already dead?

And in verse 25 we read that the livestock was indeed killed.


  25 Throughout Egypt hail struck everything in the fields—both people and animals; it beat down everything growing in the fields and stripped every tree.


So we discussed this, and thought well, maybe the ten plagues took place over a longer time so the Egyptians could restore their livestock. However this seems not really possible as Moses did die at 120 years old (Deuteronomy 34:7) where Moses was 80 years old (Exodus 7:7) when he was called by God. 

What would be a good explanation for this conflict?
Answers in Genesis, an Apologetics site dedicated to defending the Bible as inerrant, gives five "reasonable" possibilities:  Bear in mind that the real answer is, "we don't know for sure", and we can't answer what did happen. The best we can do is offer plausible explanations of what might have happened.  Typically this is done using common rules behind resolving alleged Biblical discrepancies.  So, from an Apologetic standpoint, their answers do offer plausible resolutions to the apparent conflict.


  First, Exodus 9:3 states, “"Behold, the hand of the Lord will be on
  your cattle in the field, on the horses, on the donkeys, on the
  camels, on the oxen, and on the sheep—a very severe pestilence."”
  Surprisingly, this verse does not mention one of the most important
  domestic animals at that time—the goat.1 Therefore, it is possible
  that all of the livestock except goats were killed in the first plague
  on the livestock (fifth plague overall), and in the second instance it
  was goats that were affected by the plague of hail.
  
  Second, Exodus 9:19–20 mentions that those who “"feared the word of
  the Lord among the servants of Pharaoh"” were told to get their
  livestock out of the fields. Some scholars mention that these
  Egyptians may have been warned about the previous plague of pestilence
  (although it was not recorded), so they still had all of their
  livestock left. In this scenario, God warned them to put all of their
  livestock in barns so they wouldn’t be killed by hail.
  
  The third possibility is similar to the previous explanation except
  that the survival of their livestock hinges on the phrase “servants of
  Pharaoh.” Perhaps this means they were not actually Egyptians, but
  other vassal subjects who were warned of the plagues so that their
  animals could be spared. So in Exodus 9:6, where it says that all the
  livestock of Egypt died, this view suggests that the animals belonging
  to these foreign vassals were spared if they obeyed God and not
  Pharaoh.
  
  Fourth, the Bible does not reveal how much time passed between the
  fifth plague and the seventh plague. Following the fifth plague, which
  wiped out the livestock of Egypt, the Egyptians may have taken some of
  the livestock belonging to Israel. Another possibility is that they
  bought (or took) livestock from surrounding areas (Libya, Ethiopia,
  Canaan, etc). The first option would require very little time to
  complete while the second would probably require at least a few weeks.
  But since the Bible does not specify how much time passed, either is
  possible.
  
  The fifth, and perhaps simplest solution, would be to acknowledge the
  fact that “all” does not always mean exclusively “all.”2 We must use
  the context to determine its meaning. In the case of Exodus 9:6, it
  might be best translated that “"all manner of livestock of the
  Egyptians died."” In other words, the plague included all kinds of
  animals, as clarified in the third verse: “"on the horses, on the
  donkeys, on the camels, on the oxen, and on the sheep—a very severe
  pestilence."” This is the approach taken in Coverdale’s translation,
  and the New English Translation includes a footnote with a similar
  explanation.



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