Liberal scholarship on the Tenakh subscribes to something called the JEDP theory, or Documentary Hypothesis.
JEDP refers to the idea that the Torah, the Law of Moses, wasn’t composed by Moses, but rather, was the result of thousands of edits over several centuries, merging and harmonizing independent sources: the Jahwist, Elohist, Deuteronomist, and Priestly sources.
This form of higher criticism suggests the the Torah didn’t reach it’s final form until about 450 BCE.
This idea can be shocking to a lot of believers. Most conservative bible scholars categorically reject this idea, seeing as how it undermines the reliability of Scripture.
How does it undermine the reliability of the Scriptures?
By claiming some books have been heavily edited and are therefore less reliable. “Oh, Leviticus should be taken with a grain of salt, seeing how it wasn’t formed until long after Genesis, having undergone many redactions to harmonize it with the other books!”
Another example is how the theory claims the “book of Torah” King Josiah discovered in 1 Kings was actually a new book, written by one of the JEDP sources, which didn’t get merged in until later, thus rendering the record of the historical books of the Tenakh unreliable.
Additionally, the words of Yeshua and the disciples are undermined, as they understood Moses to be the principal author of the Torah, e.g. “Moses wrote to you saying…”, “…on Moses, whom you have set your hope”, etc.
The idea that the Torah was the result of 500+ years of redactions and harmonizing generally doesn’t inspire confidence in the reliability of God’s word.
In the following video. Messianic scholar J.K. McKee explains this theory and why it’s important for you, the regular Messianic folk, to be aware of this view and understand it, that you can give an adequate answer to those criticizing the Scriptures.