The Pasuk that commands us to count Sefiras HaOmer (VaYikra 23:15) says “U’Sfartem Lachem MiMochoros HaShabbos”; you should begin your count the day after Shabbos.
Chazal teach us that this doesn’t mean after Shabbos but rather after the first day of Pesach. If so why does the Torah say MiMochoros HaShabbos?
Rav Levi Yitzchok in the Kedushas Levi answers that the whole world was created because of Am Yisroel. Since there was no Am Yisroel before Yetzias Mitzrayim, up until then it was unclear why Hashem created the world. Just like Shabbos was the day Hashem completed the work of building the entire world in deed (Maaseh), so too Pesach was the day that Hashem finished the Machshava of the world. It was on that day that the creation became clear to the entire world. OurShabbos is the lower Shabbos while Pesach is the upper Shabbos the Shabbos of Machshava and the spiritual completion of the Bria.
This explains the Chazal (Shabbos 118b) that says that if Bnei Yisroel keeps two Shabbosos they will immediately be redeemed. One Shabbos refers to the physical Shabbos where we refrain from doing Melacha on the seventh day of the week. The second refers to the “spiritual” Shabbos, which is kept when we perform Hashem’s will, making His name clear and obvious to everyone in the world.