1)
Why does the Torah specify that "Chag ha'Sukos" shall be "for Hashem"?
1.
Rashi (in Sukah 9a) and Targum Yonasan: To teach us that one should celebrate Sukos for the sake of the Mitzvah. 1
2.
Targum Onkelos: 'Celebrate the Yom-Tov of Sukos ... before Hashem'.
3.
Sukah 9b: To teach us that, just as the Name of Hashem (Kedushah) takes effect on the Korban Chagigah, so too, does it take effect on the Sukah - and the wood of the Sukah is therefore Asur b'Hana'ah throughout the seven days of Sukos. 2
