The book of Job was written before God chose the Israelites, as His chosen people, during the time when there was no covenant which could possible save Job or for Job to have restored contact with God, which Adam lost (Gen 3:22).
Death reigned from Adam to Moses, even over those who had not sinned according to the likeness of the transgression of Adam (
Rom 5:14)
Therefore the author of Job wasn't a Jew. However,
salvation is of the Jews (
John 4:22, Rom 3:2).
The book of Job cannot be scripture and that cannot be refuted by opinion.
Q; When was the book of Job written?
A;
,
May 27, 2003
When was the book of Job written? How do we know it was written then since we don’t know who wrote the book and when Job lived?
Top Ten Reasons Why We Believe the Book of Job was Written During the Time of the Patriarchs
1. Job lived 140 years after his calamities (42:16). This corresponds with the lifespans of the patriarchs. For example, Abraham lived 175 years.
2. Job’s wealth was reckoned in livestock (1:3; 42:12) which was also true of Abraham (Gen. 12:16) and Jacob (Gen. 30:43).
3. The Sabeans and Chaldeans (Job 1:15, 17) were nomads in Abraham’s time, but in later years were not.
4. The Hebrew word (qsitah) translated “piece of silver” (42:11) is used elsewhere only twice (Gen. 33:19, Josh. 24:32). Both times are in reference to Jacob.
5. Job’s daughters were heirs of his estate along with their brothers (Job. 42:15). This was not possible later under the Mosaic Law if a daughter’s brothers were still living (Num. 27:8).
6. Literary works similar in some ways to the Book of Job were written in Egypt and Mesopotamia around the time of the patriarchs.
7. The Book of Job includes no references to the Mosaic institutions (priesthood, laws, tabernacle, special religious days and feasts).
8. The name (sadday) is used of God 31 times in Job (compared with 17 times elsewhere in the Old Testament) and was a name familiar to the patriarchs.
9. Several personal and place names in the book were also associated with the patriarchal period. Examples include (a) Sheba – a grandson of Abraham, (b) Tema – another grandson of Abraham, (c) Eliphaz – a son of Esau, (d) Uz – a nephew of Abraham.
10. Job was a common West Semitic name in the second millennium B.C. Job was also a name of a 19th-century-B.C. prince in the Egyptian Execration texts.
Kerby Anderson
Probe Ministries
Since the book of Genesis is credited to Moses. (according to the Bible) Moses was a descendant of Abraham through Isaac, Jacob and Joseph. Circumcision of the flesh was given to Abraham which started the family tree and line of inheritance that the Hebrews claim. The Law Moses Received from Yahweh would not have been written till at least 500 years after Abraham many scholars believe that the authorship of Job predates Genesis and thus Job also predates mosaic law. It wouldn't have been necessary for Job to have to have been a descendant of Abraham to be true or saved.
It never says anywhere that those uncircumcised who were born before Isaac lost anything or that any things happened to contradict any other book of the Bible. If Job wasn't a Jew so what? 
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