The Book of the Law was written by Moses and placed in the ark of the covenant of the LORD your God. (Deuteronomy 31:24-29)
Joshua added to the Book of the Law of God. (Joshua 24:26)
Higher Criticism
There are similarities between Moses' written law (1500-1400 era) and the Code of Hammurabi (circa 1780) like "eye for eye; tooth for tooth," leading to questions as to whether he copied from that source, whether certain laws are obvious to derive, or if it's mere coincidence. It's even possible that, if God had given Adam and Eve laws, people lived so long back then that people could share and discuss those laws directly with their ancestors of several generations.
(Origin of the Bible class notes, March 1, 2023. Pink jaguar print composition book. Page 1, Origin of the Bible class notes, March 23, 2023. Pink jaguar print composition book. Page 1)