Here is How it Is

We can talk about the mark of the beast all day long, but at the end of the day, you will need to decide whether to keep the Ten Commandments (including the sabbath) or not.

LawDay of worshipJudgment
Ten CommandmentsSabbathSeal of God
LawlessnessSundayMark of the beast

The mark of the beast = knowingly keeping Sunday instead of Sabbath.