Back in the Old Testament, in the book of Genesis, in the Garden of Eden, God created the entire universe in just six literal days. On the seventh day, He rested. When Abraham’s people, the Israelites went out of Egypt, God told them to keep the Sabbath, the seventh day holy.
Why is Sabbath important? God commanded the Israelites to rest and not work in their fields, not to just sleep all day. This day of rest is a day of worship and remembrance of God. True rest cannot be achieved without God.
In our time, Sunday is the rest day, and some people use it to sleep, binge watch, go to the malls, etc. However, they are missing the point of rest, and that is remembering and worshipping God.