The custom is for a person drinking wine in the presence of others to preface the Beracha of Hagefen with "Savri Maranan" (Pay attention, my masters!) to which they respond "L’haim" (to life!).
Many explanations have been offered for this custom. Rav Shlomo Luria (1510-1573) explains that the origin of this custom dates to the times when wine was used to calm the nerves of mourners and criminals facing capital punishment. Thus, the declaration "L’haim" serves to distinguish the current drinking from those morbid situations.
Mahram Mintz (Rabbi Moshe Halevi Mintz, Germany, 1415–Poland, 1480) explained that originally, wine brought curse to world. When Noach left the ark and became intoxicated, his son Ham took advantage of him, and Noach cursed his offspring. Thus, "L’haim" is said to declare that this drinking should bring only blessing, not curses.
Rabbi David Abudraham (14th Century, Seville) suggests that the fruit of the Tree of Knowledge in Gan Eden was, according to some opinions, wine. Therefore, the custom is to wish life in contrast to the original consumption of wine, which brought death to the world. In a similar vein, the Gemara in Megila records the story of Raba and Rav Zera who became intoxicated on Purim, and one sage slaughtered the other one. Thus, there is a need to affirm that this wine should not lead to negative results.
The Midrash Tanhuma states that in olden times it was common to use a wine taster to insure that no poison was added to the wine. This may also be a reason to wish life on the drinker.
Of course, there are esoteric reasons for this custom in the teachings of the Kabbalah, as well.
Nowadays, the custom is to say "L’haim" only when making Kiddush on Shabbat and Yom Tob. Rabbi Haim Palachi (Turkey, 1788-1869) explains that this may be connected to the passage that states that those who are scrupulous to observe the Misva of Kiddush will be granted long life in this world and the next.
SUMMARY
When reciting the Hagefen in Kiddush, the custom is to preface the Beracha with "Savri Maranan," to which all present answer "L’haim."
