Mark S. Smith, The Priestly Vision of Genesis 1 (Minneapolis, MN: Fortress Press, 2010), 127:
The priestly narrative style seems to come by way of priestly ritual style and background. This ritual sensibility seems to have informed Genesis 1’s style. Thus, the seven days of the festivals may have given rise to the idea of the structure of seven days in Genesis 1. The account’s literary architecture combines repetition from day to day, and at the same time it varies this expression between days. This style seems to echo the repetition of rituals, with their counting of days and their repetitions of various actions. Even with their variations within repetition, the formulations of the days and their counting, not to mention their blessing, casts God in the role of the priest of his cosmic temple, namely the universe. This ritual, priestly background may be the inspiration for the repetitive and precise style of formulation in Genesis 1. This narrative is thus better seen as having emerged out of the tradition of priestly ritual literature and not from traditional folkloristic literature. This does not mean that the priestly tradition ignored such traditional storytelling, whether in poetry or prose. Indeed, a good case has been made for Genesis 1 as showing the rhythm of biblical poetry, such as we see in traditional biblical hymns. At the same time, the composer of Genesis 1 arguably drew as well on the rhythm of ritual.
The Amateur Exegete 