What does Paul teach about how believers should regard days?
Paul teaches that believers should not regard one day as higher than another but should regard every day alike. No day, including Sunday, is set above the other six as a special holy day. Every day is alike for the believer, and God is to be served equally Monday through Friday as on Saturday and Sunday.
Les explains that the book says nothing about practicing a system of worship in this age of grace, because Christ nailed all that to His cross and we are now free. In Romans 13, Paul says not to regard one day higher than another but to regard every day alike, and that is where believers are. While there is nothing against Sunday per se, even Sunday is not taught in Scripture as a special holy day above the other six days. Paul merely said that as believers come together and bring their offerings, they do so on the first day of the week, resurrection day. But setting Sunday up as a day above all others is not taught. Every day is alike for the believer, and we are to serve God just as much Monday through Friday as Saturday and Sunday. This has all been nailed to His cross. The same legalistic tendency appeared in Galatia, where Judaizers convinced Gentiles they had to keep the Law for salvation, and Paul admonished them not to become legalists.