“Remember the Sabbath day, to keep it holy. (Exodus 20:8) [ESV]
זכור את־יום השבת לקדשו
The Qal form of the verb זָכַר in this verse means to remember or recall. An example of an nearly identical use is found when Moses restated the command to observe the Passover:
Then Moses said to the people, “Remember this day in which you came out from Egypt, out of the house of slavery, for by a strong hand the LORD brought you out from this place. No leavened bread shall be eaten. (Exodus 13:3)
...ויאמר משה אל־העם זכור את־היום הזה
The people were to remember something they had experienced.
The Ten Commandments were given at Mount Sinai in the third month (19:1). The command to observe the Sabbath by not gathering manna had been given on the 15th day of the second month (16:1). Therefore the people would have observed at least two Sabbaths (on the 22th and 29th) before receiving the Ten Commandments: they were to remember that which they experienced.
Their experience with the Sabbath began with the manna, which was given to test if they would walk in the law of the LORD (16:4). In conjunction with the quail, the people would know it was the LORD who brought them out of Egypt (16:6) and He was the LORD their God (16:12). On the seventh day the people were to eat the manna they had gathered and prepared on the sixth day because it was a day of solemn rest, a Sabbath to the LORD (16:23):
27 On the seventh day some of the people went out to gather, but they found none. 28 And the LORD said to Moses, “How long will you refuse to keep my commandments and my laws? 29 See! The LORD has given you the Sabbath; therefore on the sixth day he gives you bread for two days. Remain each of you in his place; let no one go out of his place on the seventh day.” 30 So the people rested on the seventh day. (Exodus 16)
The Sabbath the people were observing was a specific day of the week. The command at Sinai was not a principle of working six days and resting one; it was a command to remember the specific day of the week they had been resting. They were to continue to keep it holy (set apart). For those who the LORD brought out of Egypt, the Sabbath day was a practice of not working on the specific day the LORD demonstrated by not giving manna.
The command at Sinai does three things. First, it memorializes a specific day of the week. Second, it adds the element of corporate rest. Where the command on gathering the manna might be construed as applying to individual action, the command at Sinai requires the head of household to ensure rest for all, including animals. Third, it gives the reason for choosing a seven-day period composed of six days of work: that is how the LORD created.
Thus, the command at Sinai illuminates the command to observe the Passover:
On the first day you shall hold a holy assembly, and on the seventh day a holy assembly. No work shall be done on those days. But what everyone needs to eat, that alone may be prepared by you. (Exodus 12:16)
The people were already familiar with a seven-day period. However, unlike the Sabbath, the seven-days to remember the Exodus adds a day of rest at the start. With the creation cycle in view, the day of rest at the beginning of the seven-days of Unleavened Bread is a remembrance the LORD freed them from bondage.
1. For those brought out of Egypt, the Sabbath was observed on the day which no manna fell. Unlike some contemporary interpretations of the Sabbath command, it could not be obeyed on a day of their choosing.