40 On the first day you shall take the product of hadar trees, branches of palm trees, boughs of leafy trees, and willows of the brook, and you shall rejoice before Hashem your God seven days.
ul-kakh-TEM la-KHEM ba-YOM ha-ri-SHON p’-REE AYTZ ha-DAR ka-POT t’-ma-REEM va-a-NAF aytz a-VOT v’-ar-VAY NA-khal us-makh-TEM lif-NAY a-do-NAI e-lo-hay-KHEM shiv-AT ya-MEEM
מ וּלְקַחְתֶּם לָכֶם בַּיּוֹם הָרִאשׁוֹן פְּרִי עֵץ הָדָר כַּפֹּת תְּמָרִים וַעֲנַף עֵץ־עָבֹת וְעַרְבֵי־נָחַל וּשְׂמַחְתֶּם לִפְנֵי יְהֹוָה אֱלֹהֵיכֶם שִׁבְעַת יָמִים׃
23:40 You shall rejoice before Hashem your God seven days
Sukkot, the Feast of Tabernacles, was the most joyous of the festivals observed in the Beit Hamikdash. According to the Sages (Rosh Hashana 16a), on Sukkot, however, Hashem judges the people for water and determines how much rain will fall in the coming year. Given the fact that Eretz Yisrael is very dependent on rainfall, it seems that Sukkot should be a solemn time and not one of joyous celebration. What is the reason for such festivity? By making His people dependent on rainfall which comes from heaven, Hashem ensures that they must maintain a close connection with Him through prayer at all times. It is the constant connection with the Almighty, by virtue of His children’s continued dependence on Him, which is the cause for great celebration on Sukkot.