At the end of six days, God’s creation of the world is finished. This doesn’t mean that God ceases working, for as Jesus said, “My Father is still working, and I also am working” (John 5:17). Nor does it mean that the creation is complete, for, as we will see, God leaves plenty of work for people to do to bring the creation further along. But chaos had been turned into an inhabitable environment, now supporting plants, fish, birds, animals, and human beings.
God saw everything that he had made, and indeed, it was very good. And there was evening and there was morning, the sixth day. Thus the heavens and the earth were finished, and all their multitude. And on the seventh day God finished the work that he had done, and he rested on the seventh day from all the work that he had done. (Gen. 1:31-2:2; emphasis added)
God crowns his six days of work with a day of rest. While creating humanity was the climax of God's creative work, resting on the seventh day was the climax of God's creative week. Why does God rest? The majesty of God’s creation by word alone in chapter 1 makes it clear that God is not tired. He doesn’t need to rest. But he chooses to limit his creation in time as well as in space. The universe is not infinite. It has a beginning, attested by Genesis, which science has learned how to observe in light of the big bang theory. Whether it has an end in time is not unambiguously clear, in either the Bible or science, but God gives time a limit within the world as we know it. As long as time is running, God blesses six days for work and one for rest. This is a limit that God himself observes, and it later becomes his command to people, as well (Exod. 20:8-11).