Leviticus 23:34
32 It is a Sabbath of complete rest for you, and you must humble yourselves on the ninth day of the month in the evening, from evening until evening you must observe your Sabbath.” 33 The Lord spoke to Moses: 34 “Tell the Israelites, ‘On the fifteenth day of this seventh month is the Feast of Shelters for seven days to the Lord. 35 On the first day is a holy assembly; you must do no regular work. 36 For seven days you must present a gift to the Lord. On the eighth day there is to be a holy assembly for you, and you must present a gift to the Lord. It is a solemn assembly day; you must not do any regular work.
1 Kings 8:2
1 Then Solomon convened in Jerusalem Israel’s elders, all the leaders of the Israelite tribes and families, so they could witness the transferal of the ark of the Lord’s covenant from the City of David (that is, Zion). 2 All the men of Israel assembled before King Solomon during the festival in the month of Ethanim (the seventh month). 3 When all Israel’s elders had arrived, the priests lifted the ark. 4 The priests and Levites carried the ark of the Lord, the tent of meeting, and all the holy items in the tent.
Notes and References
"... What did they talk about, gathered around the torah? The answer is apparently Sukkoth, the Feast of Booths. The Torah as we know it does indeed mention this feast several times. Leviticus (23:33-36; 39-44), Numbers (29:12-40) and Deuteronomy (16:13-15) contain rules and regulations concerning Sukkoth (compare also Exodus 23:16). This is an important festival, one of the three 'high holy days', also simply called גח, 'the festival' (see for instance Leviticus 23:41; 1 Kings 8:2). When we look at these - extremely disparate - texts, we observe some similarities with Nehemiah 8:13-18, but even more differences. Some regulations we do not find in Nehemiah at all, as for instance the rule regarding the offering of sacrifices (Numbers 29:12-38), or the prohibition to do slave labour (Leviticus 23:35, 36; Numbers 29:12, 35). Conversely, Nehemiah 8 mentions various matters that cannot be traced back to any of the relevant texts in the Torah, as for instance some types of foliage that do not correspond to the four traditional types mentioned in Leviticus 23:40,126 or the way in which the command to proclaim this injunction to all the towns is phrased (compare Leviticus 23:2, 4). The Nehemiah passage most closely resembles Leviticus 23, the only text from the Torah that mentions building booths, but here, too, there are differences, as for instance the instruction to build booths in the temple grounds in Nehemiah 8:16 ..."
Venema, G. J. Reading Scripture in the Old Testament: Deuteronomy 9-10, 31, 2 Kings 22-23, Jeremiah 36, Nehemiah 8 (pp. 177-178) Brill, 2004