Torah Scholars may only eat at Meals of Mitzvot: Pesachim 49a
Benefitting from a Meal which is not for a Mitzvah leads to Exile: Pesachim 49a
HaShem puts one who doesn't join a Meal of a Mitzvah in Ex-Communication: Pesachim 113b
Defining [Non-]Mitzvah Meals
The Meals of Engagement and Marriage for a Kohen's daughter and a Regular Jew, or the daughter of a Torah Scholar to a lay-person, unless he is a Torah Scholar: Pesachim 49a
Meal for finishing a section of Torah: Shabbat 118b-119a
