When a person recites Kiddush on Friday night on behalf of everybody at the table, the listeners must have in mind to fulfill their obligation with his Berachot – the Beracha of "Gefen" over the wine, and the Beracha of Kiddush. By having this intention, they are considered as though they personally recited the Berachot.
As we know, it is customary for the one who recites Kiddush to then pass the cup around the table so that everybody can drink from the Kiddush wine. It is forbidden for the people at the table to speak before they drink from the wine, just as one who recites a Beracha over any food or drink must not speak until eating or drinking. Since, as mentioned, one who listens to the Beracha is considered to have personally recited it, he must not speak until he drinks from the wine, just as the one who recited the Beracha may not speak before drinking.
This applies not only on Friday night, but anytime a person fulfills his Beracha obligation over food or drink by listening to somebody else’s Beracha. If, for example, two people sit down for a drink together, and one decides to listen to his fellow’s Beracha rather than recite it himself, he may not speak after hearing the Beracha until he drinks.
The question arises as to whether one must recite a Beracha if he spoke before drinking the Kiddush wine. It often happens that the people at the table forget the Halacha and speak after the recitation of Kiddush, before the wine reaches them. May they still rely on the Beracha they heard, or must they now recite a Beracha of their own?
Most Rishonim (Medieval Halachic authorities), including the Rosh (Rabbenu Asher Ben Yehiel, Germany-Spain, 1250-1327) and the Mordechi (Rabbi Mordechai Hakohen Ashkenazi, Germany, 1240-1298), held that one must indeed recite a Beracha in this case. According to this view, speaking in between the Beracha and drinking undermines the Beracha’s effect and thus requires the listener to recite his own Beracha. This appears to be the view accepted by the Bet Yosef (Orah Haim, 167). However, the Rama (Rabbi Moshe Isserles, Poland, 1525-1572) cites the view of the Roke’ah (Rabbi Elazar of Worms, Germany, 1160-1237) that one may still rely on the Beracha he heard, even if he spoke in the interim. According to this position, so long as the one who recited Kiddush partook of the wine without speaking in the interim, the others may rely on his Beracha even if they spoke.
As for the final Halacha, we have a famous rule of "Safek Berachot Le’hakel," which means that we do not recite a Beracha if there is some question as to whether it is warranted. In the case under discussion, then, one may drink from the wine without reciting a Beracha. It must be emphasized, however, that this applies only "Be’di’abad," in a case where one mistakenly spoke; optimally, of course, one must ensure not to speak after the recitation of Kiddush until after he drinks from the wine.
Summary: After the recitation of Kiddush, the listeners must not speak until they partake of the wine. If, however, somebody did speak in the interim, he may drink without a Beracha, so long as the one who recited the Kiddush drank without speaking in the interim.
