What is a sin is to require others to Saturday worship (a la 7th Day Adventists) in order to go to heaven.
What is a sin is to abuse Scripture and quote it just like Satan did at the temptation of Christ.
My position is that 7th Day Adventists are a cult. I have come to this conclusion only from TT. I didn't used to believe this.
For you to say the Law (which includes the one and only Sabbath) is dead or that it is a sin to keep it, contradicts the testimony of Paul. Paul himself participated in the Nazir vow. He participated in SIN SACRIFICES.