EXOD387 Sanctify the Shabbos with words. At the start and end of the Sabbath, speak of the greatness of the Sabbath and how it differs from the other days of the week. Our Sages explained that this mitzvah is performed over wine--Kiddush at the start of the Sabbath and Havdalah at the end. Performance of this mitzvah awakens us to recall the greatness of the Sabbath and internalizes our belief that Hashem created the world. The mitzvah is performed over wine because wine has unique power to stir a person's heart. These matters become a part of us through our actions and the stirrings of our hearts.