Codification in The Torah
The Torah mentions the commandments to obtain a lulav for the Sukkot holiday once in Leviticus:
Leviticus 23:40
- ולקחתם לכם ביום הראשון פרי עץ הדר כפת תמרים וענף עץ עבת וערבי נחל ושמחתם לפני ה׳ אלקיכם שבעת ימים
- "On the first day, you must take for yourself a fruit of the citron tree, an unopened palm frond (lulav), myrtle branches, and willows the brook. You shall rejoice before God for seven days."
In the Oral Torah, the Mishnah comments that the biblical commandment to take the lulav, along with the other four species, is for all seven days of Sukkot only in and around the Temple Mount when the Holy Temple in Jerusalem is extant, as indicated by the verse as "in the presence of Hashem, your God, for seven days." In the rest of the Land of Israel, as well as in the Diaspora, the four species are biblically mandated only on the first day of Sukkot. After the destruction of the Temple in 70 CE, Rabbi Yochanan ben Zakai legislated a rabbinical enactment to take the four species for the entire seven days of the holiday in all locations as a commemoration of what was done in the Temple.
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