What is "book of the law of moses"

Pentateuch \Pen"ta*teuch\, n. [L. pentateuchus, Gr. ?; ? (see Penta-) + ? a tool, implement, a book, akin to ? to prepare, make ready, and perh. to E. text. See Five, and Text.] The first five books of the Old Testament, collectively; -- called also the Law of Moses, Book of the Law of Moses, etc.