“Remember the Sabbath day.” It can be quite easy to lose track of which day of the week it is and to accidentally ignore the Sabbath, or to get so pressed with things to do that it just does not seem as important to obey the Sabbath as to get that “important” work done. People face that kind of thing all the time when they ignore some things in order to do “more important” things. In God’s eyes, Israel keeping the Sabbath was one of the things they had to remember and take time to do.
There are people who try to use the word “remember” to assert that the Sabbath had been a regular institution far back into the past, but there is no evidence for that and no reason to take the word “remember” that way. If a mother tells a child, “remember to take your vitamins,” it does not mean he or she has been taking vitamins for a long time. In this case, since the Ten Commandments were given in the third month after leaving Egypt (Exod. 19:1) and the Sabbath was introduced one month after Israel left Egypt (Exod. 16:1), then Israel had only kept something like six Sabbath days. [For more on the Sabbath, see commentary on Exod. 20:10].