According to the third of the Ten Commandments:
Remember the Sabbath day by keeping it holy. Six days you shall labour and do all your work, but the seventh day is a Sabbath to the Lord your God. On it you shall not do any work, neither you, nor your son or daughter, nor your manservant or maidservant, nor your animals, nor the alien within your gates. For in six days the Lord made the heavens and the earth, the sea, and all that is in them, but he rested on the seventh day. Therefore the Lord blessed the Sabbath day and made it holy.
The Bible provides an example to true followers of its faith, commanding them what they need to do if someone does not obey this rule:
While the Israelites were in the desert, a man was found gathering wood on the Sabbath day. Those who found him gathering wood brought him to Moses and Aaron and the whole assembly, and they kept him in custody, because it was not clear what should be done to him.
Then the Lord said to Moses, "The man must die. The whole assembly must stone him outside the camp." So the assembly took him outside the camp and stoned him to death, as the Lord commanded Moses.
- Numbers 15:32-36
If there is such a thing as a Sabbath Day, that special day which God has chosen for us to worship, then what day is it?
To many Christians, the Sabbath day is Sunday.Yet to Seventh-Day Adventists, they insist that the Sabbath Day is Saturday.
To Muslims however, it is Friday:
O you who believe, when the Congregational Prayer (Salat Al-Jumu`ah) is announced on Friday, you shall hasten to the commemoration of GOD, and drop all business.
- Koran 62:9
Obviously, the Sabbath Day is very important if a man can be killed for not observing it. Yet even here, religions do not agree on such an important detail.