“Moses was teaching the people that in order to create a Sanctuary for God in this world, a place where man and God could meet and commune, it needed to be infused first and foremost with the holiness of Shabbat.
As important and positive the six days of work are, they ultimately receive their blessing from Shabbat. This can be seen in the words of the beloved song Lecha Dodi sung universally at the beginning of Shabbat: ‘The end of deed [Shabbat] is the first in thought.’
This idea can be seen in one of the permutations of the first word of the Torah, bereishit, (בראשית) being yirah-Shabbat (ירא-שבת), ‘the awe of Shabbat.’ Although Shabbat was the last in creation it was first in thought, encoded ‘in the beginning.'”