Apologies but time does not permit me to expand on this. These are notes:
-- here we are, finally ready to build the Mishkan (Tabernacle) which is to house the presence of G-d (the Shechina).
-- oops. before we go into all the activities ... one thing, says Hashem. In the middle of all the preparations and excitement of finally building the Mishkan, Hashem, says "Stop. Remember the Sabbath."
What's that got to do with the context??
There are many explanations, chief among them that the reference to Sabbath, followed by all the various activities required to build the Mishkan teaches us the thirty-nine basic forms of work not allowed on the Sabbath. That's why the reference to Sabbath is there.
I say there's something else going on here. These are the people who after hearing G-d speak the first commandment of having no other gods before Him, went out and made a Golden Calf, and worshipped it, a mere forty days later. Looks like they forgot. The Mishkan they are about to erect is a kaparah (atonement) for that sin, and is designed to bring G-d back into their midst.
So G-d is using this interpolated moment suddenly referring to the Sabbath to remind the people who they are, and to assure them that atonement is at hand through this act of forgiveness, and their slate is clean and they are starting over.
How does the reference to the Sabbath remind the people of who they are?
What is the first reference to Israel in the Torah?
It's not anything to do with Jacob. The first reference in the Torah to Israel is clearly, unequivocally, encoded in the story of Creation. At the end of the Sixth Day, "Yom Hashishi" starts an amazing little code with big significance. We say this part over every Friday night when making Kiddush.
If you take the "Yud" at the end of the word "Shishi," which denotes the end of the week of Creation," and you count seven letters (for the seventh day, perhaps?), you get an "S." Count seven more letters, and you get an "R." Count seven more letters, and you get an "A." Count seven more letters, and you get an "L." Vowels in Hebrew are below the letters, so these letters, in Hebrew, if not quite in English, spell out what? "Israel."
G-d dedicated the very first Shabbos to Israel, and tied Israel inexorably to Shabbos, thereby.
To remind the Children of Israel of the Shabbos at a time when they were trying to re-establish their relationship with G-d, is to tell them (a) G-d is willing to start over, right back to the Beginning, and (b) their job is to remember who they are -- the people chosen by G-d to keep the Sabbath, Israel. It's back to first principles. G-d knows who we are. We sometimes forget. G-d's mention of the Sabbath is our reminder, full of acceptance and encouragement.
