Many people today work for 5 days and rest on the other 2 days of the week. Even if we are no longer under the Old Testament Law; is it a contradiction to God's design, where the people were supposed work for 6 days (Exodus 20:9) and rest for 1 day weekly?
For thousands of years prior to the giving of the Old Law, men worked seven days a week. The concept of not working one day a week was new with the giving of the Law. "The LORD did not make this covenant with our fathers, but with us, those who are here today, all of us who are alive" (Deuteronomy 5:3). Even with this new concept, the Israelites were unique in this practice. "And what great nation is there that has such statutes and righteous judgments as are in all this law which I set before you this day?" (Deuteronomy 4:8). The Gentiles continued to work seven days a week.
The concept of a five day work week started in the very early 1900's by Henry Ford [HENRY FORD: Why I Favor Five Days' Work With Six Days' Pay]. There is nothing inherently right or wrong with the concept. In the New Testament God requires that men work for a living (II Thessalonians 3:10). He did not specify how many hours per week or how many days per week.