Did Moses copy the Old Testament from another book or source?   If the last statement is true then would that mean that the only reliable thing in the Bible are in the New Testament?

First of all, Moses was only responsible for a limited portion of the Old Testament.  Almost certainly he did not write Genesis.  There is no evidence that he did, and the book has evidence of sources in Mesopotamia, not Egypt.  Moses did not write any book after Deuteronomy.  So, the only books he had a hand in are Exodus through Deuteronomy.  Even these books he did not write entirely.  The books do not have a definite seal of authorship.  Moses certainly did not write the very last portion of Deuteronomy!  I do believe that certain portions of Exodus through Deuteronomy were written down originally by Moses, or it is possible some were spoken by him orally and written down by others.

You ask whether Moses copied parts of the Old Testament from another book or source.  This questions confuses me, to be honest.  What part of Exodus through Deuteronomy might one propose was copied from another source?  It is possible that parts of the historical books Joshua through 2 Chronicles were taken from other historical sources, but not Exodus through Deuteronomy, as these are principally historical books.  Such is not the case with the Mosaic books, although there is some historical material.  Please, perhaps you can help me.  What portion of Exodus through Deuteronomy would you propose that Moses might have copied from another source so I can comment?

Let us, for the sake of argument, propose that Moses copied certain small portions of Numbers from another historical source.  Would this make this Scripture any less reliable?  The way I see it, the question is not what are the sources, but whether the Bible is inspired by God and whether it is reliable historically.  Historians use sources. Of course they do, this makes them more, not less reliable.  What we need to do is ask these questions.  Is there evidence that the Old Testament is inspired by a supernatural God?  I say the answer is a resounding yes!  Is there evidence that the Old Testament contains reliable historical information?  Is say a resounding yes!  I have a great deal of evidence of these claims at the web site and in my books Reasons for Belief, Is There a God, Daniel, Prophet to the Nations and From Shadow to Reality.  All of them are available at www.ipibooks.com.  I urge you to consider buying and reading these books.  They demonstrate beyond a reasonable doubt that the Old Testament, broadly, is inspired by God and is reliable historically.

Getting back to your question.  I do not know of any portion of the books written by Moses in which he used other sources.  However, I do know that parts of the  Samuels, the Kings and the Chronicles use other historical sources, because the authors quote their sources, such as The Annals of the Kings of Judah.  Using reliable sources does not make the Old Testament unreliable. Again, it comes down to this: Is there sufficient evidence to reach the general conclusion that the Old Testament is inspired by God and reliable, historically?  I say a definite yes, but you will need to decide for yourself.

On a side note, the New Testament authors use the Old Testament as a source of reliable and inspired information.  2 Timothy 3:16 is a claim for such inspiration.  Therefore, if the Old Testament is not reliable and inspired, then this draws the reliability and inspiration of the New Testament into question as well.  So any attempt to say the Old Testament is not reliable, but the New Testament is reliable will fail.

John Oakes