There are essentially two concepts on who wrote the Pentateuch. The Mosaic which is that Moses wrote most of it, and that later editors made annotations and updated geographical or detailed terms; or a much later author in the sixth century wrote it all, placing original terms into the document to make it look authentic.
It is not possible that the Pentateuch can be both Mosaic in origin or was written in the sixth century. By just computing the date, Moses had written these books somewhere between 1400 and 1200 and the claim of the sixth century origin? Do the math.
Scholars are in disagreement about when the Pentateuch was composed. Some argue that it is a series of compilation from between the 10th – 5th centuries, others have argued for its creation of the 2nd century. Let us prove otherwise.
There are verses which state or strongly imply that Moses was the author. Consider the following passages in the Pentateuch itself: Exodus 17:14 “Then the Lord instructed Moses, ‘Write this down as a permanent record…’” Exodus 24:4 “Then Moses carefully wrote down all the Lord’s instructions.” Exodus 34:27 “And the Lord said to Moses, ‘Write down all these instructions, for they represents the terms of my covenant with you and with Israel.’” Leviticus 1:1 “The Lord called to Moses from the Tabernacle and said to him, ‘Give the following instructions to the Israelites…’” Leviticus 6:8 “Then the Lord said to Moses, ‘Give Aaron and his sons the following instructions…’” Deuteronomy 31:9 “So Moses wrote down this law and gave it to the priests.” Deuteronomy 31:24-26 “When Moses had finished writing down this entire body of law in a book…”
These are passages elsewhere in the Hebrew Scriptures on where we can see the authorship of Moses: Joshua 1:7-8 “…Obey all the laws Moses gave you.” Joshua 8:31-34 “He followed the instructions that Moses the Lord’s servant had written in the Book of the Law…” Joshua 22:5 “…Obey all the commands and the laws that Moses gave to you.” 2 Chronicles 34:14 “…Hilkiah the high priest…found the book of the Law of the Lord as it had been given through Moses.”
We even have passages in the Gospels which show that Jesus and John the Baptizer believed Moses to be the author: Matthew 19:7-8 “…why did Moses say a man could merely write an official letter of divorce and send her away?”, they asked. Jesus replied, ‘Moses permitted divorce…’” Matthew 22:24 “Moses said, ‘If a man dies without children…’” Mark 7:10 “For instance, Moses gave you this law from God…” Mark 12:24 “…haven’t you ever read about this in the writings of Moses, in the story of the burning bush…” Luke 24:44 “…I told you that everything written about me by Moses and the prophets and in the Psalms must all come true.” John 1:17 “For the law was given through Moses…” John 5:46 “But if you had believed Moses, you would have believed me because he wrote about me. And since you don’t believe what he wrote, how will you believe what I say?” John 7:23 “…do it, so as not to break the Law of Moses…”
Other passages in the Christian Scriptures: Acts 26:22 “…I teach nothing except what the prophets and Moses said would happen…” Romans 10:5 “For Moses wrote…”
I believe in the inerrancy of the Bible, the matter of authorship is settled and is not open to debate. Moses was the human author of Genesis and the other books of the Pentateuch. These five ‘books of the law’ were written by Moses alone. The Pentateuch, therefore, is an inspired, inerrant, authoritative document written by the man Moses.