Megillah, Chapter Three, Mishnah Five
This mishnah lists the portions read on the three pilgrimage holidays, Pesah, Shavuot and Sukkot and on Rosh Hashanah and Yom Hakippurim as well.
Most of these are straightforward and do not require explanation.
The one slightly confusing issue is the readings for Sukkot. On the first day of Sukkot we read from Leviticus 23, the same reading as on Pesah. On the remaining days we read the sacrifices listed for that day in Numbers 29:17 ff. Sukkot differs from Pesah in that on Pesah the same musaf offerings are made every day. On Sukkot each day has a different number of offerings. As an aside, this is one reason why we recite the full Hallel for all seven days of Sukkot but only on the first day of Pesah.
1) On Pesah we read from the portion of the festivals in Leviticus (Torat Kohanim) (Leviticus 23:4).
2) On Shavuot, Seven weeks (Deuteronomy 16:9).
3) On Rosh Hashanah On the seventh day on the first of the month (Leviticus 23:23).
4) On Yom Hakippurim, After the death (Leviticus 16).
5) On the first day of the Festival [of Sukkot] they read from the portion of the festivals in Leviticus, and on the other days of the Festival [of Sukkot] the [sections] on the offerings of the Festival.