WHEN DOES A CHATZIZAH INVALIDATE IMMERSION OR CONVERSION? [Tevilah:Chatzitzah]
Question: Rava said that if a (pregnant) Nochris converted, her child need not immerse. What is the reason?
Answer: It is due to R. Yitzchak's law:
(R. Yitzchak): Mid'Oraisa, a Chatzitzah (interruption) invalidates Tevilah only if it covers the majority, and he is Makpid (bothered by it. The fetus does not mind that his mother surrounds him, so her Tevilah is also Tevilah for him.)
Objection: Rav Kahana taught that this is when the Chatzitzah covers a majority, but if the entire body is covered the Tevilah is invalid!
Answer: A fetus is different. Since he grows in his mother, she is not a Chatzitzah.
Nidah 67b (R. Yitzchak): Chachamim invalidate the immersion if there is a Chatzitzah on the majority and he is not Makpid, or a Chatzitzah on the minority that he is Makpid about, due to a majority he is Makpid about.
Question: Why didn't Chachamim decree about a Chatzitzah on the minority that he is not Makpid about, on account of minority he is Makpid about?
Answer: A minority he is Makpid about is only a decree. We do not decree to guard a decree!
Rambam (Hilchos Isurei Bi'ah 13:7): If a pregnant woman immersed and converted, her child need not immerse
Rambam (Hilchos Mikva'os 1:12): There may not be a Chatzitzah on a person or Keli that blocks him or it from the water. If there was a Chatzitzah, e.g. dough or mud stuck to the skin or Keli, he or it is still Tamei; the Tevilah did not help. Mid'Oraisa the Tevilah does not help if the Chatzitzah was on the majority of the person or Keli and he was insistent to remove it. If he did not care about it, or if it covered the minority even if he cared about it, the Tevilah was valid. Mid'Rabanan, if anything he cares about interrupted, the Tevilah did not help, even if it covered the minority. This is a decree due to such a Chatzitzah on the majority. Mid'Rabanan, a Chatzitzah on the majority invalidates Tevilah even if he did not care about. This is a decree due to a Chatzitzah on the majority that he cares about. If a Chatzitzah such as dough or pitch was on the body, even the size of a mustard seed and he cares about it, the Tevilah was invalid. If he does not care, the Tevilah was valid, unless it covered the majority of the person or Keli.
Question (R. Akiva Eiger): Why did the Rambam omit that a Chatzitzah that covers the entire body is mid'Oraisa?
Rambam (2:15): One tied hair is a Chatzitzah if he is Makpid about it.
Rosh (Chulin 8:15 b'Sof): Rashi (Eruvin 4b DH Rubo) says that a Chatzitzah invalidates Tevilah mid'Oraisa if it covers the majority, i.e. of the hair. R. Tam (Tosfos 4b DH Devar) proved that a Chatzitzah on the majority of the body is also a Chatzitzah.
Question (Rosh Hilchos Mikva'os (after Perek 9 of Nidah) 26): A Tosefta says that a tight ring is a Chatzitzah. Why is this? It is a minority that one is not Makpid about it (to remove it)!
Answer (Rosh, citing the Ra'avad): She is Makpid to remove it when she kneads. Since she is Makpid at some times, it is a Chatzitzah even if she is not Makpid when immersing.
Mishnah (Mikva'os 9:3): We are concerned for Chatzitzos in the underarm and Beis ha'Starim (covered places) in a man, but not in a woman;
R. Eliezer says, we do not distinguish men from women. It is a Chatzitzah only if he is Makpid.
Shulchan Aruch (YD 268:6): If a pregnant Nochris converted, her child need not immerse.
Dagul me'Revavah: If Beis Din knew that she was pregnant, the law is obvious. If not, this is a complex matter.
Beis She'arim (YD 362 DH v'Kol): According to Tosfos in Kesuvos (11a DH Matbilin), Beis Din is Zocheh for a minor, so Beis Din must know that she is pregnant. According to Tosfos in Sanhedrin (68b DH Katan), a minor is Zocheh for himself, so Beis Din need not know.
Aruch ha'Shulchan (11): Tosfos (Bava Kama 47a DH Mai) rules that a fetus is like a limb of his mother, in any case her immersion helps for him.
Yachel Yisrael (89 DH v'Hinei): The Dagul me'Revavah's doubt was whether or not a fetus is considered part of his mother!
Pischei Teshuvah (6): Tif'eres l'Moshe says that if she did not convert, the immersion did not help for her son.
Shulchan Aruch (198:1): She (a Nidah) must immerse her entire body at once. Therefore, there cannot be any Chatzitzah, even any amount. And if it is normal for people to be Makpid about it sometimes, it is a Chatzitzah even if she is never Makpid about it, since others are Makpid about it.
Beis Yosef (DH Oh): Her opinion is Batel to most people's opinion. If not, Tevilah is subjective! I am unsure about when most people are not Makpid and she is. It seems that the Rambam and Rashba argue about this. The Rambam (Hilchos Mikva'os 2:15) says that one tied hair is a Chatzitzah if he is Makpid about it, even though it is known that most people are not Makpid. It seems that the Tur agrees. He says that most people are not Makpid about dirt and dough under fingernails, so they are Chotzetz only for one who is Makpid about them. The Rashba (Toras ha'Bayis ha'Katzar 31b) says that if hairs are knotted individually so much that women are normally Makpid about this, they are a Chatzitzah. This implies that it does not depend on her herself. The Rambam discussed only the person herself. He did not say that it depends at all on most people. Perhaps his is a third opinion.
Taz (3): The Bach and the Darchei Moshe citing the Mordechai say that it is a Chatzitzah.
Gra (3): R. Eliezer and Chachamim argue (Mikva'os 9:3) about whether or not we are concerned for the person himself, or for most people.
Taz (2): The Shulchan Aruch connotes that if a minority of people are Makpid and she is sometimes Makpid it is a Chatzitzah even if now she is not Makpid. If most people are Makpid it is a Chatzitzah even if she is never Makpid.
Shach (1): Since she is sometimes Makpid, even if most of the time she is not, it is always Chotzetz.
Shulchan Aruch (ibid.): If it covers the majority of her body it is a Chatzitzah even if people are not normally Makpid about it.
Rema: L'Chatchilah she should not immerse even with things that are not Chotzetz lest she immerse with things that are Chotzetz.
Taz (4): The Gemara said that we do not decree to guard a decree, i.e. b'Di'eved. L'Chatchilah we do.
Shulchan Aruch (202:2): Anything that people are normally Makpid about is a Chatzitzah (on a Keli). If not, it is a Chatzitzah only if it covers the majority.
Rema: Blackness stuck to the outside of a pot is like the wall of the Keli. It is normal; it is not a Chatzitzah.
Taz (3): If it is on the inside it is a Chatzitzah, if people are normally Makpid about it.