Priestly Source

The Priestly source (or simply P) is, according to the documentary hypothesis, one of four sources of the Torah, together with the Jahwist, the Elohist and the Deuteronomist. The characteristics of the Priestly source include a set of claims that are contradicted by non-Priestly passages and therefore uniquely characteristic: no sacrifice before the institution is ordained by God at Sinai, the exalted status of Aaron and the priesthood, and the use of the divine title El Shaddai before God reveals his name to Moses, to name a few.

P was written to show that even when all seemed lost, God remained present with Israel.

The history of exilic and post-exilic Judah is little known, but a summary of current theories can be made as follows:

The Pentateuch or Torah (the Greek and Hebrew terms, respectively, for the bible's books of Genesis, Exodus, Leviticus, Numbers and Deuteronomy) describe the history of the Israelites from the creation of the world, through the earliest biblical patriarchs and their wanderings, to the exodus from Egypt and the encounter with God in the wilderness. The books contain many inconsistencies, repetitions, different narrative styles, and different names for God. There are, for example, two accounts of the creation, two genealogies of Seth and two of Shem, two covenants with Abraham and two revelations to Jacob at Bethel, two calls to Moses to rescue the Israelites from Egypt, two sets of laws at Sinai, and two accounts of the Tabernacle/Tent of Meeting. The repetitions, styles and names are not random, but follow identifiable patterns, and the study of these patterns led scholars to the conclusion that four separate sources lie behind them.

...
Wikipedia