R’ Yishmael says: Three myrtle twigs, two willow twigs, one lulav, and one esrog [are required]; even if two are broken off and one is not broken off. R’ Tarfon says: Even if all three are broken off.  R’ Akiva says: Just as there is one lulav and one esrog, so [there is] one myrtle twig and one willow twig.

A stolen esrog or a dry one is invalid.  [One] from an asherah or from a city that was led astray is invalid.  [One] of orlah is invalid.  [One] of contaminated terumah is invalid. [If it is] of pure terumah he should not use it, but if he used it, it is valid.  [If it is] of demai, Beis Shammai invalidate it, and Beis Hillel validate it.  If it is of maaser sheni in Jerusalem, he should not use it, but if he used it, it is valid.