Why are believers not required to practice the Old Testament system of worship today?

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 believers are now free. He points to Romans 13, where Paul says not to regard one day higher than another but to regard every day alike—that is where believers are. Even Sunday is not taught in Scripture as a special holy day above the other six; Paul only mentioned coming together and bringing offerings on the first day of the week, resurrection day. Les stresses that setting Sunday up as a holy day is not taught, for every day is alike for the believer, and we are to serve God just as much Monday through Friday as Saturday and Sunday. He then takes the reader back to Galatians 4, where Paul wrote because Judaizers were convincing Gentiles they had to keep the Law to experience salvation; Paul admonished them not to fall under the temptation to become legalists. Les says this is no different today, since legalism appeals to the human ego, but God will have none of it.