"Remember the sabbath day, to keep it holy." (Exodus 20:8)
The Hebrew word shabbat is found 108 times in the Old Testament. The basic meaning is "intermission" or "break." The term never means "Saturday" or "seven."
The pattern of resting every seventh day-night cycle was established by God at creation (Genesis 2:1-3; Exodus 20:11). God "made" (performed activity) for six days and rested and ended His work on the seventh day.
Therefore, God blessed and "hallowed" the resting day to commemorate His initial work and rest cycle. There is no other basis for this pattern. There is no relationship for the seven-day week in any astronomical clock reference: solar, stellar, or lunar. In fact, the Lord Jesus clearly told us that He made the sabbath for humanity (Mark 2:27). Apart from God's specific design, we would have no reason to observe the seven-day week, which is common to all cultures.
All humanity observes the seven-day cycle from a practical and physiological need. Christians, however, should acknowledge that the sabbath was dedicated by God at creation to be a day of "sanctification."
God's people should follow the pattern He set (Genesis 2:1-3) and recognize the wonder and majesty of the creation (Exodus 20:11). We should cease from our own profitable employment (Exodus 20:9-10) and, more importantly, concentrate on the worship of our Creator (Psalm 92).
This commandment is the only command listed with a specific reason, and the precise wording should forever settle the argument about a "day-age" interpretation of creation. In Exodus 20:11, the wording can only mean a "regular" day.
There is no linguistic excuse for long ages anywhere. HMM III