How the Hebrew Bible came into being
Image source: http://www.solveisraelsproblems.com/the-remarkable-revival-of-the-hebrew-language/
Think of the Bible the way you would a stratified archaeological site. Some of it was written in the eighth century B.C., some the seventh and then going all the way to the second B.C. So 600 years of compilation. This doesn’t mean that the story doesn’t come from antiquity. But the reality presented in the story is a later reality…. When the authors of the story describe (the golden city of Jerusalem; a great empire in the time of Solomon) they have in their eyes the reality of their own time, the Assyrian Empire.
Israel Finkelstein to Robert Draper Kings of Controversy”, National Geographic, December 2010, p 66 at 85.
The source material for the Bible began to grow by the 8th century BCE, and its core was Deuteronomy, the first part of the Hebrew Bible in writing. From the 7th to the 6th centuries BCE, the written text compiled by the scribes began to achieve equal standing with the oral traditions, and the first elements of the Torah began to emerge, its sources comprising psalms, songs, poetry, prayers, rituals and sagas and administrative records.
 Susanne Glover: WEA Hebrew Bible in crisis lecture series.