They found written in the law how the Lord had commanded through Moses that the Israelites should dwell in booths during the festival of the seventh month.
Nehemiah 8:14 In-Context
Then all the people went away to eat and drink, to send portions of food and to celebrate with great joy, because they now understood the words that had been made known to them.
On the second day of the month, the heads of all the families, along with the priests and the Levites, gathered around Ezra the teacher to give attention to the words of the Law.
They found written in the Law, which the LORD had commanded through Moses, that the Israelites were to live in temporary shelters during the festival of the seventh month
and that they should proclaim this word and spread it throughout their towns and in Jerusalem: “Go out into the hill country and bring back branches from olive and wild olive trees, and from myrtles, palms and shade trees, to make temporary shelters”—as it is written.
So the people went out and brought back branches and built themselves temporary shelters on their own roofs, in their courtyards, in the courts of the house of God and in the square by the Water Gate and the one by the Gate of Ephraim.