Nehemiah 8:13-15

13On October 9 the family leaders of all the people, together with the priests and Levites, met with Ezra the scribe to go over the Law in greater detail.

14As they studied the Law, they discovered that the Lord had commanded through Moses that the Israelites should live in shelters during the festival to be held that month.

15He had said that a proclamation should be made throughout their towns and in Jerusalem, telling the people to go to the hills to get branches from olive, wild olive, myrtle, palm, and other leafy trees. They were to use these branches to make shelters in which they would live during the festival, as prescribed in the Law.