Nehemiah 8:13-15

13On the second day, the heads of the families along with the kohanim and the Levites gathered around Ezra to ponder the words of the Torah.

14They found written in the Torah that Adonai had commanded through Moses that Bnei-Yisrael should dwell in sukkot during the feast of the seventh month.

15So that they should proclaim and spread this message in all their towns and in Jerusalem saying, “Go out to the hill country and bring olive branches and wild olive branches, myrtle branches, palm branches and branches of other leafy trees to make sukkot, just as it is written.”