The Sabbath was created at creation and it is the fourth commandment given to ALL of Humankind. It is the only commandment that begins with the word "REMEMBER".
It appears that GOD knew that people would forget and HE instructed us to REMEMBER the SABBATH and to keep it HOLY!
This is about is "WORSHIP" and the day we have been instructed to worship on. The Sabbath means "seventh" day and Saturday is the seventh day.
The majority of Christians worship GOD on Sunday. They do not realize that Sunday is not the day of worship and if it is Saturday why do so most churches have worship services on Sunday?
Answers can be found by checking out the following documents (PDF):
Here is a 12 minute video that gives some clear and concise information on The Sabbath click here.