A seudat mitzvah (סעודת מצוה, "commanded meal"), in Judaism, is an obligatory festive meal, usually referring to the celebratory meal following the fulfillment of a mitzvah (commandment), such as a bar mitzvah, bat mitzvah, a wedding, a brit milah (ritual circumcision), or a siyum (completing a tractate of Talmud or Mishnah). Seudot fixed in the calendar (i.e., for holidays and fasts) are also considered seudot mitzvah, but many have their own, more commonly used names.
Attendance at a brit milah (circumcision) and its subsequent seudah is of such great significance that Rabbi Moshe Isserles ("the Rama") notes that a Talmudic saying that one who is invited but does not participate in the seudat brit milah is ostracized by God. For this reason, people are generally not invited, but merely informed of the brits time and location. Talmudic sages have compared a brit to a Temple sacrifice, and eating at a seudat brit milah to eating a Temple sacrifice. Hasidic Jews generally insist on serving meat at a seudat brit milah since most Temple offerings were meat. Sharing a meal is considered a bonding experience celebrating the covenant between God and the Jewish people.
Pidyon HaBen
Unlike other seudot mitzvah in which the meal (seudah) follows the act or ceremony which warrants the festive meal, the redemption ceremony for a first-born Jewish male child (called Pidyon HaBen in Hebrew), is actually part of the meal. The ceremony is led by a kohen, who ritually washes his hands, recites the blessing over bread, and partakes of some bread before beginning the ceremony. The ceremony, which follows a traditional text, is a verbal exchange between the kohen and the father of the child. The kohen asks the father if he prefers to keep his money, or pay the equivalent of five silver shekels to redeem his child. The father chooses the latter option and hands over the money, as well as recites a special blessing ("al pidyon haben"). Then the kohen''' verbalizes the redemption, blesses the child, and says the traditional blessing over a cup of wine, which he then drinks.