Lulav and Etrog
It is written in the Book of Vayikra, 23:40,
“You shall take for yourselves on the first day -
the fruit of a citron tree, the branches of date palms, twigs of a platted tree, and brook willows
The Rabbis explain that this verse refers to the Lulav, Etrog, Hadas and Aravah.
Therefore, on the festival of Sukkot we ‘take’ -
  • the Lulav (a branch from the centre of a date palm),
  • the Etrog ( a specific citrus fruit),
  • 3 branches from the Mertyl tree and
  • 2 Willow branches, to fulfil the Mitzvah (commandment) of Lulav and Etrog.
Although the commandment from the Torah is only for ‘the first day’,
the Rabbis instituted the custom of taking the Arba’at Hamininm (four species) on all 7 days of Sukkot.
 
 
 
 
It is also said that the four species represent 4 different types of Jews.
The Etrog, which has a beautiful scent and taste, represents someone who learns Torah and does Midot Tovot (good deeds).
The Lulav, which has no scent but a nice taste, represents a person who learns Torah, but lacks good deeds.
The Hadas, which has a beautiful scent, but no taste, represents a person who does good deeds but lacks Torah.

Finally, the Aravah, which has no taste or scent, represents a person who neither learns Torah or does good deeds.
These four types of people all exist within the Jewish nation. By bringing the four species together, it is a symbol of bringing all types of Jews together.
According to Jewish tradition, regardless if a Jew is a great Tzaddik (righteous person) and Talmid Chacham (learned person), or a simple, ordinary person, it is important that the Jewish nation has Achdut (unity), and come together as one. Only then, tradition says, will the final redemption of the Jewish people transpire.
 
 
 
 
 
 
 
 
Thanks to Rafi Karp of Bnei Akiva Melbourne