The Torah says:

"You shall take... the beautiful fruit (Esrog), a palm frond (Lulav), myrtle twigs and willow branches of the stream -- and rejoice for seven days before the Lord your God." (Leviticus 23:40)

On Sukkot, we bind all the branches together -- two willows on the left, one palm branch in the center, and three myrtles on the right. We hold this bundle in our right hand, and then lift them together with the Esrog. We then shake them all together, three times in each direction: front, right, back, left, up and down. (Sefardim and Chassidim have a different custom for the order.) This mitzvah should be performed during the daytime, each of the seven days of Sukkot (except for Shabbat).

Before waving the four species, we say the following blessing:

"Baruch ata Adonoy, Elo-heinu Melech ha'olam, asher kid'shanu bi'mitzvo-sav, vi'tzivanu al ni-tilas lulav."

Blessed are You, Lord our God, King of the Universe, who sanctified us with His mitzvot, and instructed us to raise up the Lulav.

To be valid for the mitzvah, the four species must meet certain requirements. Since the details are many and technical, it is not recommended to search through the forest on your own for these species! (Particularly the Esrog, which can easily be confused with a lemon.) A better idea is to purchase a complete set from a reliable distributor. Your local Jewish bookstore may have a "Four Species Set" with a rabbinical seal certifying their validity.

To be an informed consumer, here are some basic requirements to look for:

• Should preferably be turning yellow rather than green.

• The peel cannot be punctured through in any spot, nor can it lack any of its inner skin.

• The peel cannot be overly soft, cracked, dry or peeled.

• Even a small black dot on the upper part invalidates it.

• The shape should preferably be like a tower - wider at the bottom and narrow at the top.

• If this particular Esrog grew with a protruding stem (called a pitom), then that stem cannot be broken off. (However, if the Esrog grew in the first place without a pitom, it is still kosher.)

• You will need three myrtle branches.

• A kosher myrtle has a pattern of three leaves coming out from the same point in the branch. This three-leaf pattern must be repeated over at least half the length of the branch.

• Each branch should be at least 11 inches (29 cm.) long.

• The branch cannot be dried out.

• You will need two willow branches.

• The stem should preferably be red.

• The stem should be at least 11 inches (29 cm.) long.

• The leaves should be oblong, not round in shape.

• The leaves should have a smooth edge, not serrated.

• Look at the very top of the branch and make sure that the center-most leaf is not split, but rather is closed (at least half-way down).

• The top cannot be cut off.

• The branch cannot be dried out.

• It should be at least 16 inches (39 cm.) long.

• The straighter the branch, the better.

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