In this week's Sedra, we read about the creation of the world. On every day of the week of creation, the Torah states: ... שני ,ויהי ערב ויהי בקר יום אחד, until it finally reaches the sixth day. Rashi asks why the letter ה"" was added to Friday, thus saying יום הששי. He offers two interesting answers:
A) Hashem added the letter on the sixth day with the completion of the world in order to tell us that he created the world on the condition that Bnai Yisrael would accept upon themselves the five books of the Torah.
B) יום הששי, All the days were dependent upon the sixth day which represents the sixth day of the month of Sivan, the day God revealed the Torah to Am Yisrael.
The Gemara in Avoda Zara 3a tells us that the reason for the extra "ה" is to show us that the Torah is actually referring to the most important day in history. The sixth of sixth of Sivan in the year 2,844, we are being told that the creation is only complete when Bnai Yisrael accepted the Mitzvot at Har Sinai. The world can not exist without Torah, and had Bnai Yisrael not accepted the Torah, God forbid, the world would have turned to תהו ובהו, void and nothingness.
The Lubavitcher Rebbe has stated that Shabbat Breishit is special because it affects the entire year, and the tone set on Shabbat Breishit carries through the rest of the year. The question is what makes this Shabbat so unique? Why shouldn't the same apply to that all important day of Matan Torah? He answers that this Shabbat relates to all matters whether physical or spiritual and it affects the whole year because etymological, the word שנה, year, is related to the word שנוי, change. When one realizes that everything comes from Hashem, only then can one bring upon a change in oneself.