Naso Likutei Sichos vol 8 page 49 ff. Shabbos (1) Class One.In this first class the Rebbe argues that although there is this presumption that Shabbos happens all by itself, it still requires Yidden to count. And if they don’t there isn’t Shabbos.His proof is from the Halacha that someone who loses track of time...

Likutei Sichos vol 8 page 49 ff. Shabbos (1) Class Two.The Rebbe stresses that if no one counts there is no Shabbos, not because Shabbos is one Nekuda (like The Rogetchover); Moreover, the count must be a “Mitzva count” and otherwise it doesn’t matter even if it was counted.This is proven by the example of...

Likutei Sichos vol 8 page 49 ff. Shabbos (1) Class Three.The uniqueness of the FIRST Shabbos after Mattan Torah.