third book of the Latin Vulgate Bible, the name of which designates its contents as a book (or manual) primarily concerned with the priests and their duties. Although Leviticus is basically a book of laws, it also contains some narrative (chapters 8–9, 10:1–7, 10:16–20, and 24:10–14). The book is usually divided into five parts: sacrificial laws (chapters 1–7); the inauguration of the priesthood and laws governing their office (chapters 8–10); laws for ceremonial purity (chapters 11–16); laws governing the people's holiness (chapters 17–26); and a supplement concerning offerings to the sanctuary and religious vows (chapter 27).

Scholars agree that Leviticus belongs to the Priestly (Priestly code) (P) source of the Pentateuchal traditions. This material is dated according to one theory in the 7th century BC and is regarded as the law upon which Ezra and Nehemiah based their reform. Older material, however, is preserved in P, particularly the “Holiness Code” (chapters 17–26), dating from ancient times.

Because the closing chapters of the preceding book (Exodus) and the opening chapters of the following book (Numbers) are also P materials, the existence of Leviticus as a separate book is presumably a secondary development. This hypothesis suggests that Leviticus properly belongs to a larger literary unit that is variously understood to include the first four, five, or six books of the Old Testament.