Prior to the nineteenth century, Christians had little interpretive guidance outside of the biblical text itself. Christians gave little or no attention to Jewish biblical scholarship, and less to the collected writings found in the Midrash. But in the last century alone, archaeological discoveries of inscriptions and even entire libraries written in the oldest known scripts in the world have totally changed how modern scholars view the ancient biblical texts.
Most ancient societies assigned ritual and magical significance to various numbers. In Mesopotamia, the number three reflected the separation of the cosmos into the heavens, the earth, and the underworld. The Sumerian conception of a square earth, also lent significance to the number four. The number seven was the most commonly revered number. Gods came grouped in sevens, rituals had to be repeated seven times, and so on. In the oldest known literary text, “The Epic of Atrahasis,” the creation of humanity is at the hand of the womb-goddess Mami, also called Nintu, who mixed the blood of a sacrificed god with clay. She divided the clay into seven pairs of bricks- seven males and seven females. The Genesis parallels are striking. First is the substance of the creation, clay or “dust of the earth” and the introduction of some portion of the divine in humanity either by blood or by breath. The next parallel with the seven pairs of “clean” animals in the Genesis Flood narrative taken aboard the Ark is obvious. It is particularly striking as the “Epic of Atrahasis,” Tablet III is the original flood myth introduced to the Bible through the Akkadian “Epic of Gilgamesh” Tablet XI.
The celebration of a seventh day Shabbat, or holy day of rest, was first introduced biblically in Exodus. In Exodus 16, Manna is given to the people each day, and they are commanded to only collect the amount they can use in a single day. On the sixth day they are given the commandment to collect and prepare enough Manna for two days, for they are not to do any work- not even to cook or light a fire- on the seventh day. They are to hold this seventh day as a “Shabbat” or day of worship. Specifically, the Hebrews were instructed to rest and give thanks to YHWH for being rescued from Egypt and sustained in the wilderness, Ex 16:22-30. This is the first biblical mention of a special observance for a seventh day Shabbat. Most significantly, it does not mention anything regarding the creation week.
A different reason for a seventh day observance is given in Exodus 20:8-11, and simply reiterated in Exodus 31:13-18;
8. Remember the Sabbath day, to keep it holy.
9. Six days shalt thou labor, and do all thy work:
10. But the seventh day is the Sabbath of the LORD thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy manservant, nor thy maidservant, nor thy cattle, nor thy stranger that is within thy gates:
11. For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the LORD blessed the Sabbath day, and hallowed it.
The commandment to honor a seventh day Shabbat in Ex 34:21 and 35:2-3 do not make reference to the creation, but the observance of a Feast of Unleavened Bread found in Ex 34:18, re-emphasizes the ritual significance of the number seven and the escape from Egypt. More over, Deuteronomy 5:12-15 explicitly states that the purpose of the seventh day Shabbat is to give rest to servants and to honor the exodus account given in Ex 16.
From extra-biblical sources, the seven-day week replaced a ten-day week formerly used as a standard following the Egyptian astrologers "discovery" that the five planets observable by the naked eye, plus the Sun and Moon could be assigned as the astrologically dominant influence for each day. This was remarked on by Herodotus, who writing in his History during the 5th century B.C. said: "Here are some other discoveries of the Egyptians. They find...each day belongs to a god..." and also, “The Egyptians were the first to assign each month and each day to a particular deity …” The Egyptians held that the nearest “planet” to Earth was the Sun, and the furthest was Saturn. They accordingly ordered their seven day week from this as Sun, Moon, Mars, Mercury, Jupiter, Venus and the seventh day was dedicated to Saturn. (An ordering based on the assignment of each of 24 hours to a god, with the day dominated by the god associated with the first hour of a day, yields the same sequence of days, but is not attested in any ancient authority that I know of.) Each planet was associated with a god, and this is still reflected in the common English names for the days of the week with Norse gods replacing four of the ancient Mediterranean ones. The Hebrew Sabbath on the seventh day was first associated by the ancient Egyptians with the most distant planet/god Saturn, or Satur(n’s)+day. (An ordering based on the assignment of each of 24 hours to a god, with the day dominated by the god associated with the first hour of a day, has been proposed that yields the same sequence of days, but is not attested in any ancient authority that I know.)
Modern biblical scholarship recognizes that the first chapter in Genesis is a late addition to the Bible. The prior existance of a pagan seven day week had to be accomidated by the Hebrews, and two different efforts were introduced, the earliest in Exodus 16. The later, probably dating to the post exilic period, was the seven day creation week which is given a total of two sentences of biblical support.