The Priestly writers who are thought to have written many passages in Exodus were the last of the “big four” writer/editor/redactors of the Torah, the first five books of the Hebrew Bible.

The "Big Four" Groups of Writers of the Torah

The first three writer groups were the J writers – so called for their name for God, Yahweh (or Jehovah) – of the Davidic and Solomonaic monarchies around 1000 BCE; E writers —for Elohim, another God name – of the Northern Kingdom which fell to the Assyrians in 720 BCE; and the D Writers – named for their authorship of Deuteronomy – just before and after the fall of the Southern Kingdom in 587 BCE and the beginning of the exile into Babylon. Scholars call this last group “Priestly” because they are concerned about liturgy, cult issues, purity laws and the Levite (priestly) succession and power. Aaron, Moses' brother, was a Levite, and the P writers beef up his part in Exodus pretty obviously, especially in the genealogy in Exodus 6:14-27.

The P Writers Wrote for the Babylonian Exiles

The P writers did their work – collecting texts and traditions, writing, editing, redacting and making the five books of the Torah into a new whole – at the end of the exile of the Southern Kingdom in Babylon, around 450 BCE to perhaps as late as 150 BCE. Thomas Thompson notes in Journal for the Study of the Old Testament that the P writers may have been writing about traditions that could have been 300 years old, trying to rouse some enthusiasm among the exiles for their “home,” and their home religion.