You shall make yourself the Festival of Sukkoth…] when you gather in [the produce]-: [i.e.,] at the time of the ingathering, when you bring the summer fruits into the house. Another explanation: “when you gather in [the produce] from your threshing floor and your vat” (בְּאָסְפְּךָ מִגָּרְנְךָ וּמִיִּקְבֶךָ) teaches that we should cover the sukkah [only] with the waste products that come from the threshing floor and the vat [i.e., with things that have grown from the ground, have become detached, and are not susceptible to ritual uncleanness. Since they are not foods and are not vessels, they are not susceptible to spiritual uncleanness. - R.H. 13a; Suk. 12a]
14And you shall rejoice in your Festival-you, and your son, and your daughter, and your manservant, and your maidservant, and the Levite, and the stranger, and the orphan, and the widow, who are within your cities.
15Seven days you shall celebrate the Festival to the Lord, your God, in the place which the Lord shall choose, because the Lord, your God, will bless you in all your produce, and in all the work of your hands, and you will only be happy.
and you will only be happy: According to its simple meaning, this is not an expression denoting a command, but rather an expression of an assurance [i.e., I promise you that you will be happy]. But according to its oral interpretation, [our Rabbis] learned from this to include the night before the last day of the Festival for the obligation of rejoicing. — [see Suk. 48a; Sifrei]
16Three times in the year, every one of your males shall appear before the Lord, your God, in the place He will choose: on the Festival of Matzoth and on the Festival of Weeks, and on the Festival of Sukkoth, and he shall not appear before the Lord empty-handed.
and he shall not appear before the Lord empty-handed: But bring burnt-offerings of appearance (עוֹלוֹת רְאִיָּה) [which are obligatory when appearing before the Lord in Jerusalem on the Festivals] and Festival peace-offerings. - [Chag. 8b]
[Every] man [shall bring] as much as he can afford: One who has many eaters [i.e., a large family] and many possessions should bring many burnt-offerings and many peace-offerings. — [Sifrei; Chag. 8b]