The Talmud on the Four Species

b. Menaḥot 27a

And [with regard to the] four [species] of the lulav, [each prevents fulfillment of the mitzvah with the others, as the verse states]: And you shall take (Leviticus 23:40), [which alludes to]: A complete taking, [comprising all four species. . . . The Gemara] raises an objection [from a baraita: With regard to the] four species of the lulav, two of them, [the lulav and etrog,] produce fruit, and two of them, [the myrtle and willow,] do not produce fruit. Those that produce fruit have a bond with those that do not produce fruit, and those that do not produce fruit have a bond with those that produce fruit. And a person does not fulfill his obligation [of taking the lulav] until they are all [bound together] in a single bundle.

And so too, [when] the Jewish people [fast and pray] for acceptance [of their repentance, this is not accomplished] until they are all [bound together] in a single bundle, as it is stated: It is He that builds His upper chambers in the Heaven, and has established His bundle upon the earth (Amos 9:6).

b. Sukkah 37b

And Rabbah said: [One takes the] lulav [bound with the other two species] in the right [hand] and the etrog in the left. [The Gemara explains:] What is the reason [for that arrangement]? These [species constitute] three mitzvot, and this [etrog] is [only] one mitzvah. [One accords deference to the greater number of mitzvot by taking the three species in the right hand.] R. Jeremiah said to R. Zerika: What is the reason [that] we recite the blessing only [with the formula]: About taking the lulav, [with no mention of the other species? R. Zerika said to him:] Since it [is] highest of them all [and the most conspicuous, the other species are subsumed under it. R. Jeremiah asks:] And [if that is the only reason,] let him lift the etrog [higher than the lulav] and recite the blessing [mentioning it. R. Zerika] said to him [that he meant]: Since [the tree] of its species is the tallest of them all, [it is the most prominent, and therefore it is appropriate for the formula of the blessing to emphasize the lulav].