76:23 Let’s say that one made a mistake on yom tov and, instead of saying “Mekadesh Yisroel v’hazmanim” (that G-d sanctifies Israel and the seasons), he said “Mekadesh haShabbos” (that G-d sanctifies Shabbos). If he immediately corrected himself, he has fulfilled his obligation. If not, he must go back and resume from the bracha of “Atah b’chartanu.”
77:1 There is a positive mitzvah in the Torah to sanctify Shabbos with words, as it says, “Remember the Shabbos day to sanctify it” (Exodus 20:8). This means that we should talk about Shabbos by making Kiddush at the start of Shabbos and havdalah at its conclusion. (There is a difference of opinion as to whether the obligation to recite havdalah is Biblical or rabbinic in origin – Mishnah Brurah 296:1.) The Sages instituted to recite both of these prayers over a cup of wine.