Exodus 20:8

Remember the Sabbath day, to keep it holy.

Presupposes an acquaintance with the Sabbath, as the expression "remember" is sufficient to show, but not that the Sabbath had been kept before this. From the history of the creation that had been handed down, Israel must have known that after God had created the world in six days he rested the seventh day, and by his resting sanctified the day (Genesis 2:3). But hitherto there had been no commandment given to man to sanctify the day.-- Keil. It has been alleged that the word remember may be reasonably explained in one of two ways without adopting the inference which has been mentioned. It may either be used in the sense of keep in mind what is here enjoined for the first time, or it may refer back to what is related in chapter 16, where the Sabbath day is first noticed, in giving the law for collecting the manna.-- Canon Cook.

To keep it holy.

By devoting the day to sacred purposes and refraining from secular occupations. Verses. and 10 show how the day is to be kept holy.