The fact that the Lord created the universe in six days is not to be underestimated. After all, Almighty God could have made the universe in an instant, as some of the ancient philosophers thought. He could also still have been in the process of bringing it into being after 13.787±0.02 billion years, as indicated from the best current measurements and models of astronomers. However, Scripture tells us specifically, repeatedly, and in no uncertain terms that the Holy Trinity created everything that is seen and unseen in six days, and that after declaring it very good, rested on the seventh day. As God does nothing on a whim, He must have a good reason why He did it in that specific time. By pondering this mystery we as the pinnacle of His creation will be better able to live in accordance with His will.
Fortunately, we need not wonder long about why the Lord created in this way. Moses records for us that in His Third Commandment the Lord said, “Remember the Sabbath day, to keep it holy. Six days you shall labor, and do all your work, but the seventh day is a Sabbath to the Lord your God. On it you shall not do any work, you, or your son, or your daughter, your male servant, or your female servant, or your livestock, or the sojourner who is within your gates. For in six days the Lord made heaven and earth, the sea, and all that is in them, and rested on the seventh day. Therefore the Lord blessed the Sabbath day and made it holy” (Exodus 20:8-11).
This Law of God is imprinted on creation itself. From ancient times, various peoples from all over the world have been keeping a seven day week. One can easily observe that the moon takes 29.5 days to complete a lunation. The four quarters of the phases of the moon are close to seven days in length, making a natural cadence for any culture using the moon as its calendar.
Even more so, though, the six days of work and one day of rest has deeper meaning for human and natural flourishing. While various cultures have had different weeks, for example the ancient Romans having an eight day week, and the ancient Chinese and Egyptians having ten days, yet still eventually all of these cultures coalesced on a seven day week. Modern attempts to move away from the seven day week have failed. See the famous French Republican Calendar or the early Soviet calendar. The seven day week is ingrained into creation as a natural cadence. It is good, right, and salutary for man, animals, and all creation to work and study for six days and then to rest on the seventh.
Profounder still is what our Lord and Savior Jesus Christ does with this natural cadence. In the week of His Passion He does His primary work on the day of the creation of man, thereby ending the sin of the old Adam, and emerging as the new Adam. That new Adam has His sabbath rest in the tomb. He then bursts forth to work His new creation on the eighth day, the first day of the new week. In this new pattern we continue week to week, still resting from our work every seventh day but with the first day of the new creation, Sunday, the Day of Resurrection, being our day of rest.
Thus it behooves us to be attentive to the creative work of our Lord, both His first work of creation, and His new work of recreation. Rather than end our week with the Lord’s rest, as new men in Christ we begin with it. We receive His abundant blessings of life and salvation in the Divine Service. We rejoice with our brothers and sisters in the faith in the study of the Word, being attentive to His ministers who preach that Word to us. We then go forth from the day of rest into the good works the Lord has prepared for us in our vocations. In our studies and in our lives, we are diligent in our work. We explore this vast cosmos, till the ground, build our homes, and help our neighbors. We do these works of love for our neighbors and for God because He first loved us. Then the next week we gather yet again together to be absolved of our sin, and hear once again of the excellencies of God.
All of this, and much more, is wrapped up in that very first week of creation. Why the Lord deliberately took the time and effort to execute His divine plan in seven days; why He took the same time and effort in our recreation during His Passion; why it is very good for us to learn and live in this pattern of seven day weeks which He creates and sustains us in.