Luláv cárich eged

A stolen or a dried up lulav is invalid. One [that came] from an asherah tree or from a condemned city is invalid. If its top was broken off or its leaves were detached, it is invalid. If its leaves are spread apart it is valid. Rabbi Judah says he should tie it at the top. The thorny palms of the iron mountain are valid. A lulav which is three handbreadths in length, long enough to wave, is valid.

The Laws of Taking The Lulav and Its Blessings, 15 Seifim: 1. The mitzvah of the four species is for every individual to take one lulav, two willow branches, and three myrtle branches (and in a place where there is no valid myrtle, one non-trimmed branch is sufficient (Beit Yosef 646 quoting Orkhot Hayyim)). It is a mitzvah to bind them together with two bindings, one on top of the other, to make it nicer. One can use a different material [that is not one of the four species] to bind them. If the leaves under the binding fell out such that they interpose [between one of the species and binding] there is no concern (as one species does not [problematically] interpose itself. Therefore, one should be careful to remove the string that is often tied around the myrtle (Mahari"l)). If one did not bind it during the day [before Sukkot] or if the binding became undone, it is not possible to rebind it on Yom Tov with a real knot. Rather, one should merely loop around it. RAMA: There are those who suggest making the tie in a different way, wrapping around the three species, and then inserting the head of the wrapper into the loop (Tur), and this is the practice. The practice is to attach the myrtles slightly higher than the willows (Mahari"v). The myrtle and willow should be inserted deep enough into the lulav binding such that one can pick up all three in their hand while making the blessing (Mahari"l). There are those who suggest making three bindings on the lulav, and this is our practice (Mordechai ch. "Lulav haGazul").

On a related note, the Gemara asks: Who is the tanna who taught in the baraita: There is a mitzva to bind the myrtle and the willow with the lulav, and if he did not bind it, it is fit? Whose opinion is it? If the baraita is in accordance with the opinion of Rabbi Yehuda, when he did not bind it, why is it fit? If it is in accordance with the opinion of the Rabbis, what mitzva did he perform? The Gemara answers: Actually, it is in accordance with the opinion of the Rabbis. And the reason that there is a mitzva to bind them is due to the fact that it is stated: “This is my God and I will glorify Him [ve’anvehu]” (Exodus 15:2), which they interpreted to mean: Beautify yourself [hitna’e] before Him in the performance of the mitzvot. The Rabbis agree that although failure to bind the three species does not render the lulav unfit for the mitzva, the performance of the mitzva is more beautiful when the lulav is bound.

§ The Sages taught: If the binding of the lulavwas untied on the Festival, one may bind it again. One may not bind it with a sophisticated knot as before, but with a knot like the one used in a binding of vegetables, by merely winding the string around the species. The Gemara asks: But why merely wind it? Let him tie a bow, which is permitted on Shabbat or a Festival, as he is not tying an actual knot. The Gemara answers: Whose opinion is it in thisbaraita? It is the opinion of Rabbi Yehuda, who says that a bow is a full-fledged knot, and therefore it is prohibited to tie one on the Festival.

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