Now, you're asking about the difference between the Old and New Testaments (covenants). Jesus did away with the external form of the law, including the Sabbath Day regulations. For example, he and his disciples were going through a wheat field, and his followers were picking the heads of wheat and eating them, a practice allowed by the law. But the Pharisees had set up over 600 rules about the law. They criticized the disciples for their practice as being harvesting on the Sabbath. However, Jesus said that the law was made for humans, not humans for the law. That is, human need was a higher principle than outward regulations. The four principles on the Sabbath (now the Lord's Day) that I see in the laws about the Sabbath are group worship, physical rest from daily work, and love for neighbor--all adding up to love for God, the highest principle. It's up to each person's conscience as to what shape those activities take, beyond group worship (Romans 14), but the inner principles of the Old Testament's laws carry over to the New Testament. I hope this answer helps you.