And you shall rejoice in your festival, you and your son and your daughter and your manservant and your maidservant and the Levi and the stranger and the orphan and the widow who are within your gates.
English: "And you shall rejoice in your festival" — from the moment you are obligated in the Chagigah you are obligated in rejoicing; this teaches that the night of the first festival day is exempt from the obligation of rejoicing.
On the daf / in context: The obligation of simchah begins only when the Chagigah may be offered, i.e., on the day itself.
Type of Learning
Derash on the verse (Yerushalmi) — the first night is exempt from simchah.
What Is Learned
There is no obligation of festival rejoicing on the night of the first day of the festival.