Book of Deuteronomy have given various answers to the problem. The Deuteronomistic history theory is currently the most popular (Deuteronomy was originally just the law code and covenant, written to cement the religious reforms of Josiah, and later expanded to stand as the introduction to the full history); but there is an older theory which sees Deuteronomy as belonging to Numbers, and Joshua as a sort of supplement to it. This idea still has supporters, but the mainstream understanding is that Deuteronomy, after becoming the introduction to the history, was later detached from it and included with Genesis-Exodus-Leviticus-Numbers because it already had Moses
Book of Leviticus have concluded that the Pentateuch received its final form during the Persian period (538–332 BC). Nevertheless, Leviticus had a long period of growth before reaching that form. The entire book of Leviticus is composed of Priestly literature. Most scholars see chapters 1–16 (the Priestly code) and chapters 17–26 (the Holiness code) as the work of two related schools, but while the Holiness material employs the same technical terms as the Priestly code, it broadens their meaning from pure ritual to the theological and moral, turning the ritual of the Priestly code into a model for the relationship of Israel to