"It is a sign between me and the children of Israel for ever: for in six days the Lord made heaven and earth, and on the seventh day He rested, and was refreshed. And He gave unto Moses, when He had made an end of communing with him upon mount Sinai, two tables of testimony, tables of stone, written with the finger of God" (Exodus 31:17-18).
"All scripture is given by inspiration of God" (II Timothy 3:16), but this portion of Scripture was given by direct inscription of God! Moses testified: "The Lord delivered unto me two tables of stone written with the finger of God; and on them was written according to all the words, which the Lord spake with you in the mount out of the midst of the fire in the day of the assembly" (Deuteronomy 9:10). "He wrote upon the tables the words of the covenant, the ten commandments" (Exodus 34:28). Thus, out of all the Holy Scriptures, God chose to write this section, not through one of His prophets, but with His own finger! It should, therefore, be taken literally and most seriously.
It is also significant that these commandments were structured around a weekly day of rest, "remembering" God's Creation Week--six days of creating and making everything in heaven and earth, followed by a sanctified day of rest and refreshment (note also Exodus 20:8-11 and Genesis 1:31-2:3). Ever since the creation, people have observed a weekly calendar. The seven-day week (unlike the day, month, and year) has no astronomical basis at all. People keep time in weeks simply because God did! Even those who deny the six-day week of creation must observe it, for their biological rhythms are constructed that way by God. "The sabbath was made for man," said Jesus (Mark 2:27). Since God considered the truth of the literal Creation Week so important that He inscribed it Himself, we should believe this portion of His Word first of all. HMM