The Sages instituted the recitation of kiddush over wine because it is the most dignified beverage, as it provides both nourishment and good cheer. They similarly instituted that a berakha be recited over a cup of wine at other joyful mitzvot, such as betrothal, weddings (when seven blessings – Sheva Berakhot – are recited), and brit mila. The special status of wine is also expressed in the fact that a special berakha was instituted for it. Before drinking most beverages, we recite the general berakha of She-hakol, and after finishing the drink we recite the short berakha aĥarona, Borei Nefashot. When it comes to wine, however, we recite Ha-gafen before drinking and Al Ha-gefen afterward. Another law gives expression to the special status of wine. Although its berakha is different from that of other drinks, reciting Ha-gafen over wine exempts the person drinking from making berakhot over any other drinks.
Ideally, in order to glorify the mitzva, kiddush should be made over a fine wine, one the person making kiddush really enjoys. If wine is unavailable, one should make kiddush over bread on Friday night and over an alcoholic beverage such as beer or vodka on Shabbat day. If no such drink is available, he may make kiddush over bread during the day as well.
The recitation of kiddush over wine has profound significance. Generally, holiness comes to expression in the spiritual world in a somber and serious fashion, while in the material world, the evil inclinations toward lust, arrogance, and mockery are more evident. Therefore, gentile spiritual leaders often distance themselves from joy and jubilation, as they are likely to entice one toward despicable physical desires. This is not the case for Jews. We sanctify Shabbat with wine to express the holiness of Shabbat, which reveals itself in both the spiritual and material worlds. Joy and jubilation, when properly directed, can be our true partners in revealing holiness in the world. This is the point of Shabbat – to reveal holiness through Torah study as well as festive meals, through prayer as well as kiddush over wine. This accords with the statement of the Sages: “One who recites kiddush over wine on Friday night is granted long life in this world and in the World to Come” (Pirkei De-Rabbi Eliezer 19).