Question: Where does the seven day week come from? “Then God said, "Let there be lights in the expanse of the heavens to separate the day from the night, and let them be for signs and for seasons and for days and years” (Gen 1:14). I understand that we have the moon to mark months, the sun to count off days and the stars for an accurate year, but nothing for the week?
Answer: The 7 day week is implicit in the Bible, although the Israelites were not particularly commanded to have a 7-day week prior to the exodus, nor were they commanded to hold a Sabbath day of rest. We don’t read of a Sabbath command in the Bible until we get to the book of Exodus.
We do read in the book of Genesis that God rested on the 7th day, and Adam and his descendants most probably followed God’s example, because Yahweh had spoken to Adam about it and set the process of a 7-day week for humanity in motion.
Genesis chapter 1 helps us see a little of why God broke down the narrative of the creation into 7 days i.e. humans needed to follow God’s example. Although, it's worth remembering that Moses told us that God’s day and our day may differ - "A thousand years in your sight are like a day that has just gone by, or like a watch in the night" (Ps 90:4), but the lesson is still there for us to apply to ourselves - God didn’t “command” Adam and his descendants to take a break, the Lord led by example.
Yahweh was someone whom Adam would want to emulate, so the 7-day week was a part of Adam’s life and the 7-day week would also be passed on to the surrounding Mesopotamian people because we know that they too had a 7-day week.
We can see that Cain and Abel took time off work to present Yahweh with a gift or offering - "In the course of time Cain brought some of the fruits of the soil as an offering to the LORD" (Gen 4:3). What English Bibles translate is "In the course of time" is "At the end of days" in Hebrew. Barnes' commentary says "this may denote the end of the week," and so do a number of other commentarys.
The story of Noah also has a number of allusions to 7 days. Furthermore the word “week” is actually mentioned in Genesis 29:27–28 regarding Jacob’s wife Leah completing her bridal week. Leah and Jacob were in northern Mesopotamia at the time. The Hebrew word mentioned in regard to Leah and Jacob’s week is shabua, which means a heptad: a group of 7.
At the other end of the Fertile Crescent we find that the Egyptians did not keep a single day in 7 special, and they didn’t have a 7-day week. The early Mesopotamians however, did have a 7-day week, and many people have debated why that is so. One school of thought supposes that the Mesopotamians chose 7 days for a week because of the 7 moving celestial bodies we can see with the naked eye: the Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn.
We call the days of the week after those names: Sun for Sunday, Moon for Monday, and Saturn for Saturday. Tuesday, Wednesday, Thursday, and Friday have been replaced in English with the Germanic/Norse names: Tiw for Tuesday (Mars), Woden for Wednesday (Mercury), Thor for Thursday (Jupiter), and Freya for Friday (Venus). Tiw was equated with Mars, which is why in French Tuesday is called Mardi and in Spanish it’s called Martes. French and Spanish, plus quite a number of other Romance languages, preserved the Latin names, except for Sunday which was changed to Dominicus meaning the Lord’s Day and Saturday was also changed to Sabado meaning Sabbath.
Another viewpoint is that a lunar month can be divided up into 4 quarters of 7 days each. Well, almost, but it doesn’t quite work out.
The Bible may offer another explanation why the Mesopotamians had a 7-day week. We know that Yahweh was active in southern Mesopotamia because he brought water to the area and planted a garden. He explained to the man in charge of the garden that he had created the universe in 6 days and rested on the 7th day. The man and his children, to whom Yahweh imparted this information, were held in high esteem in Mesopotamia because of their long lives. From this we understand that the Mesopotamians learned of the 7-day week through Adam and his offspring.
God spoke to the hearts of all early humans, but they had begun to go their own way, as we are told in Ecclesiastes 7:29, “God created mankind upright, but they have gone in search of many schemes.” So God highlighted his message to us through Adam and his offspring, the 7-day week being a small part of that message. God also wrote of the importance of the indivisible number 7 in the skies with the 7 moving celestial spheres. Psalm 19:1–4 explains that the night-time sky has a voice:
“The heavens declare the glory of God;
the skies proclaim the work of his hands.
Day after day they pour forth speech;
night after night they display knowledge.
There is no speech or language where their voice is not heard.
Their voice goes out into all the earth, their words to the ends of the world.”
Adam’s son Seth is reputed by Josephus to have been a fine astronomer and so he would have noted the 7 wandering celestial bodies. Names were given to these travelling lights in the sky and a temptation arose for subsequent generations to think of these physical spheres as gods, or as representing celestial beings. The Bible explains that though men have gods ruling their lives there is only one true God. Even today people will try to “read the stars,” and horoscopes are written that are thought to rule over certain aspects of people’s lives. The first book of the Bible emphasizes the number 7 with the creative days, and the last book of the Bible also stresses the number 7 with the 7 lampstands, 7 stars, 7 churches, 7 seals, etc.
Perhaps, the fact that God specifically commanded a 7th day of rest to the group of people leaving Egypt, means that both the 7-day week and the 7th day of rest had been lost to the Israelites during their tenure in Egypt and it needed to be reinstated. So, God wrote it in stone—something we may have happen in our own lives from time to time: we fail to do what is correct concerning a certain issue, so God gives us a reminder that we will never forget.
We first heard about a day of rest in Genesis 2:3, but the trail for the Sabbath day thereafter seems to go cold. The liberated Israelites were told to “Remember the Sabbath day,” as if somewhere along the line a day of rest had been lost and they needed to remember it and start applying it to their lives once more. In the story of the exodus we can see God looking for an opportunity to reinstate the 7-day week, and finding one.
Employers ought to give their employees a day off. We can’t keep on working one day after the other without a break - “You have six days each week for your ordinary work, but on the seventh day you must stop working. This gives your ox and your donkey a chance to rest. It also allows your slaves and the foreigners living among you to be refreshed" (Exod 23:12).
So we see that the 7 day week is implicit in the Bible.