Building a sukkah
ולקחתם לכם ביום הראשון פרי עץ הדר כפת תמרים וענף עץ-עבת וערבי-נחל ושמחתם לפני יקוק אלקיכם שבעת ימים: בסכת תשבו שבעת ימים כל-האזרח בישראל ישבו בסכת
You shall take on the first day an esrog fruit, palm fronds (a lulav), myrtle branches, and willow branches, and you shall rejoice before Hashem your G-d for seven days. You shall dwell in sukkos for seven days. Every citizen of Israel shall dwell in sukkos
Sukkos is known as Zman Simchaseinu, the time of our rejoicing. The days are accentuated with their unique mitzvos, that of taking the four species and dwelling in the sukkah. The Torah introduces these mitzvos in this precise order, first the four species, then dwelling in the sukkah. While the reason for this requires its own study, what’s fascinating is the Sages, when they chose the structure of their teachings on the festival, chose to first discuss the laws of the sukkah, and only then the laws of the four species. Why did the Sages switch the order from that in the Torah?