Generally speaking, a person who drinks a Rebi段t of wine must recite a Beracha Aharona ("Al Ha暖efen Ve誕l Peri Ha暖efen") after he drinks. If, however, he drinks wine as part of a meal that included bread, he does not recite a Beracha Aharona, because the Birkat Ha知azon recited after the meal covers the wine.
The Halachic authorities debate the question of whether one recites a Beracha Aharona after drinking wine at the beginning of a meal. If a person wishes to begin his meal by drinking wine, before washing his hands for bread, do we consider this drinking part of the meal, such that it is covered by Birkat Ha知azon? Or, since the individual drinks the wine before eating bread, perhaps it does not constitute part of the meal, and he must therefore recite a Beracha Aharona before he washes to eat bread.
The Shulhan Aruch (Orah Haim 174), based on the ruling of the Rosh (Rabbi Asher Ben Yehiel, Germany-Spain, 1250-1327) in Masechet Pesahim (10:24), writes that one does not recite a Beracha Aharona in such a case. In his view, since the wine is drunk as an appetizer introducing the meal, it is considered part of the meal and is therefore covered by the Birkat Ha知azon recited after the meal.
However, since other authorities disputed this ruling, Hacham David Yosef advises in his work Halacha Berura (vol. 9, p. 109) that a person should drink less than a Rebi段t of wine in this case. Since a Beracha Aharona is required only when one drinks a Rebi段t or more of wine, by drinking less than a Rebi段t one avoids this Halachic question. Of course, if one did drink a Rebi段t of wine before a meal, he should not recite a Beracha Aharona, in accordance with the Shulhan Aruch痴 ruling. Ideally, however, one who drinks wine right before a meal should make a point of drinking less than a Rebi段t.
It should be noted that this does not apply to Kiddush recited at the beginning of meals on Shabbat and Yom Tob. According to all views, the wine one drinks for Kiddush constitutes the introduction to the meal, since one may not eat a meal before reciting Kiddush. As such, all opinions agree that the Kiddush wine is covered by the Birkat Ha知azon recited after the meal, and therefore one does not recite a Beracha Aharona after drinking the Kiddush wine. Hence, one may drink as much wine for Kiddush as he wishes, since according to all views he will not be required to recite a Beracha Aharona.
Summary: When a person drinks wine at the beginning of a meal, before he washes his hands for bread, he should preferably ensure to drink less than a Rebi段t. If he drinks a Rebi段t, however, he does not recite a Beracha Aharona after drinking, since the wine is included under Birkat Ha知azon. When it comes to Kiddush, however, one may drink as much wine as he likes, and does not have to limit himself to less than a Rebi段t.
