Chatzitzah And Its Applications
‘Greater Stringency Applies To Hallowed Things…’
(Chagiga 20b-21a)
The mishnah (on 20b) states that one may not immerse two vessels kodesh one inside the other. R. Ela (on 21a) explains that the weight, or pressure, of the inner vessel against the outer vessel will prevent the mikveh water from reaching all parts of the vessels. In other words, it might be a chatzitzah.
Comparison to Lulav
A lulav must be bound with haddassim and aravos with nothing separating them. Raba submits (Sukkah 37b) that we need not be concerned if some haddas or aravah leaves fall off and separate the lulav from the haddasim or aravos since min bemino eino chotzetz – a substance of the same type does not constitute a chatzitzah.
Similar Substances
Rav Pinchas Horowitz, the ba’al HaHafla’ah, asks (Giv’as Pinchas, siman 56) why the Sages forbade immersing two sacred vessels with one inside the other. Even if they are crammed together and water is prevented from reaching parts of each vessel, we should apply the rule of min bemino eino chotzetz. Since the two vessels are of the same type, neither one should constitute a chatzitza.
An Appendage
To answer this question, Rav Horowitz postulates that a detached haddas leaf does not constitute a chatzitzah between a lulav and haddasim because the detached leaf is viewed as an appendage to the haddasim. But an impure vessel within another impure vessel is clearly not an appendage. That’s why one may not immerse the two together.