This parsha, and the first aliyah, begins on the third day after Avrohom's circumcision, when pain from surgery is at its worst, and G-d is visiting the sick by appearing to Avrohom.
During this meeting Avrohom notices that three travelers are passing by, and he runs to invite them into his home.
Avrohom is the model of hospitality. He runs to prepare food for them. (Incidentally, when he was getting calves to prepare for the meal, one calf ran away and Avrohom chased it as far as the cave of Machpella, where Adam and Chava are buried. Avrohom noticed the scent of Gan Eden there, so that's why later in the Torah he buys this property to bury his wife Sarah upon her death.)
These three travelers are really three angels, and one of them says that Sarah, Avrohom's wife, will have a son in one year.
The angels ask Avrohom where his wife Sarah is, and Rashi says one reason they asked was to pass her the Kos Shel Brocha -- the cup of blessing on the wine they held while saying the Grace after the meal. The Talmud learns from this, that passing the wine to one's wife gives tremendous blessings to her, as we see from the miraculous birth of Yitzchak soon after. The book Hayom Yom, in the entry for the date of the Lubavitcher Rebbe's wedding anniversary, encourages us to bench with wine.