WHEN DO WE SAY THAT SOAKING IS KIVUS? [Shabbos: Libun: soaking]
Gemara
128b (Beraisa): If a Yoledes needs oil [... if not, women bring oil in their hair].
Question: Also this is Chilul Shabbos, i.e. squeezing!
Answer (Rabah and Rav Yosef): Squeezing does not apply to hair.
139b (Mishnah): One may strain wine through a garment.
(Ze'iri): One may put clear wine or clear water in a Meshameres (a cloth for straining) on Shabbos without concern.
142b (Mishnah #1): If there was filth on a pillow, he may clean it with a rag;
If it is of leather, he may pour water on it until it is clean.
Zevachim 94a - Contradiction (Mishnah #2): The law of Kivus (laundering) is the same for cloth... [or leather...]
This shows that Kivus applies to leather.
Answer (Rava): "Veha'Beged... Oh Chol Kli ha'Or Asher Techaves" and our Mishnah teach that Kivus applies to soft leather. All agree to this. The Tana'im argue about whether Kivus applies to hard leather.
Question (Rava - Mishnah): If there was filth on a leather pillow, one pours water over it until it gets clean.
Answer (Rava): Kivus without rubbing is not considered Kivus. For Beged (cloth), soaking in water is Kivus.
(Rava): If one threw a turban into water (on Shabbos), he is liable.
Rishonim
Rambam (Hilchos Shabbos 22:18): If there is filth on a pillow, he may clean it lightly with a cloth. If it was of leather, he pours water on it until it is clean.
Hagahos Maimoniyos (80): If a nursing baby dirtied his mother's garment (with urine), R. Tam permitted her to wash her hands and clean (dry) them in the place of the filth [to nullify the urine], to permit her to pray. This is Derech Lichluch (the way of dirtying). The Ri disagreed, for she intends to clean the filth! If urine splashed on one's garment, the Riva permits putting water on to nullify it, for he intends to be Metaher, but not to launder and polish. We learn from a Nidah, who may scheme.
Hagahos Maimoniyos (90, citing Re'em): The Ri forbids only when there is filth, like the Beraisa discusses. I disagree. Rava obligates one who threw a turban into water. It does not mention filth! The Mishnah merely discussed a typical case. (Normally, one cleans only if there is filth.) Bahag forbids without filth; one should not clean very wet hands on wool or linen. I do not know what is considered 'much'. Therefore, on Shabbos it is good to shake the water off one's hands vigorously before drying them on a cloth. Maharam does so. Soaking is Kivus only regarding water. Wine or beer dirties the cloth.
Rosh (Yoma 8:4) and Tosfos (Shabbos 111a DH Hai): Why may one walk through a river to greet his Rebbi on Yom Kipur? Soaking is Kivus! That is only if there is blood or filth on the garment. If it darkened due to wearing or using it, and all the more so if it is white and he wants to whiten it more, soaking is not Kivus. R. Tam holds that soaking is not Kivus for something made to get dirty, e.g. drying on a towel or cleaning hands on a cloth.
Tosfos (ibid.): We are not concerned for squeezing regarding greeting one's Rebbi, or for a Nidah to immerse in her clothes, for these are Mitzvos. Going clothed through a river is Derech Lichluch.
Poskim
Shulchan Aruch (OC 302:9): One may put water on a shoe [so the filth will go away, without rubbing].
Mishnah Berurah (39): The Av Melachah of Melaben (whitening or bleaching) applies to wool, linen and all materials that whiten. Kivus and squeezing are Toldos (derivatives) of Melaben. For leather, only full Kivus is Kivus. For Beged, even if it is colored, soaking in water is Kivus. Some say so only if there is filth, but not if it merely darkened from wearing it. Then, one is liable only for proper Kivus or squeezing. Even so, mid'Rabanan one may not soak it, lest he squeeze. Some say that soaking is Kivus even if there is no filth, unless it is Derech Lichluch, e.g. drying his hands. Some are stringent to say that soaking is Kivus even Derech Lichluch if there is much water, therefore, one shakes almost all the water off his hands before drying them.
Shulchan Aruch (ibid.): If there is filth on a Beged, one may not even put water on it, for this is its Kivus.
Gra (DH she'Yesh): He cites the text of the Mishnah 'if there is filth.' It is forbidden even without filth, like the Beis Yosef says. He discusses filth to teach [after this] that one may clean it lightly with a cloth.
Beis Yosef (DH Mutar): The Mishnah forbids cleaning filth on a pillow with water, for a Stam pillow is of Beged, and putting water is Kivus. If it is of leather, he may pour water on it; for soaking is not Kivus for leather. He may not truly launder it, for Stam pillows and blankets are soft, so [full] Kivus applies. Tosfos says that soaking is Kivus only if there is blood or filth on the garment. The Rosh and Tur brought R. Tam's Heter to clean one's hands to nullify urine; but not the Ri's dissent. How does cleaning the hands help? A Revi'is is needed to nullify urine! Perhaps R. Tam permitted washing the hands over the dirty part of the Beged. The Ri agreed, for it is not normal to launder with waste (i.e. used) water. (He argued only about cleaning hands on the garment.) However, the Poskim did not mention washing over the Beged. It seems that normally only a few drops of urine leak from the baby's clothing to the mother's Beged, so it suffices to clean her hands on it.
Kaf ha'Chayim (66): The Magen Avraham (18) forbids putting any water. Likewise, one is liable for any amount of any liquid that whitens. One may not put even liquids that do not whiten in order to remove the filth. Eshel Avraham and R. Zalman obligate even for colored wool, unlike Maharam me'Rotenburg.
Bi'ur Halachah (DH Asur): The Rambam obligated one who squeezes a garment in order to extract the water, for squeezing is a need of Kivus. Squeezing does not apply to hair, and the same applies to leather. The Magid Mishneh says that he learns from 128b; the Gemara asked due to the Isur of Kivus. He did not give a source regarding leather. Nishmas Adam challenged the Rambam. Since squeezing is a Toladah of Kivus, and Kivus applies to leather, what is his source that squeezing does not apply to it? I say that he learns from the Sugya in which Rabah and Rav Yosef say that squeezing does not apply to hair. This is because it is hard. Kivus applies to even to Sak, which is made from hair (Zevachim 73b)! Even though who say that Kivus does not apply to hard leather, agree about Sak (94a. Sak includes what is made from hair of cattle and goats.) We must say that all agree that hair is not considered hard. Even so, squeezing applies only to what is very soft. Similarly, Kivus applies to soft leather, but squeezing does not. This is why the Rambam taught them together. The Gemara permits putting water on soft leather without concern for squeezing, for mid'Oraisa squeezing does not apply to it. It could have forbidden putting water on Beged lest he squeeze. It rather taught that one is liable for this, for Kivus. This answers Nishmas Adam's question. In summary, Kivus applies mid'Oraisa to hair and leather, but the Rambam holds that squeezing applies to them only mid'Rabanan. The Rema (526:1) rules that there is no squeezing regarding leather. However, Shabbos 50b forbids shampooing hair with niter and sand only lest hair fall out. Why isn't it forbidden due to Kivus? We must distinguish, and say that Kivus does not apply to attached hair on people. If so, what was the question on 128b, according to the Rambam? Since there is no Kivus, there is no squeezing! Perhaps this was the Gemara's answer, that squeezing does not apply to hair, i.e. since it is attached to her. However, the Shulchan Aruch copied the Rambam's words, and it is very hard to say that this is his intent.
Rema: One may put a small amount of water on a Beged without filth, but not much water, lest he squeeze.
Magen Avraham (19): One may put much water if he is not concerned if there is water in the garment, like it says in 301:46.
Mishnah Berurah (46): One may not put even a little water if he intends to launder.
Kaf ha'Chayim (69): Olas Shabbos says that if there is filth, it is forbidden even Derech Lichluch. If there is no filth, it is permitted only Derech Lichluch, e.g. to pass through water to go to a Mitzvah or drying with a towel.
Kaf ha'Chayim (71): Libun does not apply, since there is no filth, but we are concerned for squeezing if there is much water.
Yabi'a Omer (4 OC 30): Ketzos ha'Shulchan (6:133, 16) forbids wetting a brush to wash the body due to a Pesik Reishei of squeezing, and perhaps soaking the brush is Kivus. People keep a toothbrush clean, since they put it in their mouths, therefore we are not concerned for laundering it, like the Rema permits putting a little water on a clean garment. It seems that the Mechaber agrees. He permits drinking wormy water through a cloth (319:16). The Beis Yosef explains that soaking is Kivus only for something dirty. However, in 319:10 the Mechaber forbids water, and also in 334:24, regarding a Talis that caught fire! Darchei No'am (OC 4) says that the Mechaber holds that soaking is Kivus only if there is filth, but always forbids much water, lest one squeeze. Mishcha d'Revusa permits relying on the majority of lenient opinions, i.e. the Rambam, Rosh, Tosfos, Ran, Semag, Semak and Sefer ha'Terumah. Surely one may be lenient about hair, if there is no filth.
Rema (ibid.): Some forbid in every case.
Mishnah Berurah (47): One should be concerned for this opinion, for this is a Torah Isur.
Kaf ha'Chayim (72): This opinion holds that even if there is no filth, Libun applies, even with a little water. However, Derech Lichluch is permitted.
Kaf ha'Chayim (73): The Gra says that the first opinion is primary. Eliyahu Rabah brings many Rishonim who hold like it. However, Rishonim including the Tur hold like the latter opinion, so one should be concerned for a Torah Isur. The Acharonim hold like this.
Shulchan Aruch (319:10): One may strain clear wine or water through a Meshameres.
Beis Yosef (DH u'Mah she'Chasav d'Asur): Some say that soaking is Kivus only if there is filth. If not, there is only a decree lest one squeeze.
Rema: One may not strain water through a garment, due to Libun.
Shulchan Aruch (ibid.): Wine and others liquids are permitted.
Taz (7): The Beis Yosef (320) brings from the Ran that wine is Melaben! He proves this from a Drashah (Sukah 40a) that permits [Peros Shemitah] for eating, but not for Kivus. This requires investigation. See what I wrote in 320:12.
Magen Avraham (11): A Meshameres is made for this, so one is not concerned for laundering it. Since soaking is Kivus, we should forbid even if it is made for this! Semag and Sefer ha'Terumah say that it is because he is not concerned for its Kivus. Tosfos and the Rosh say so about a clean garment. The only Isur is a decree lest one squeeze. This applies only to water, but not to something made for this.
Gra (DH Aval): The Magen Avraham is correct. This is unlike Rav Yosef (Beitzah 18a), who forbids immersing Kelim on Yom Tov lest one squeeze. The Gemara rejected him, for a Nidah may immerse in her clothes.
Bi'ur Halachah (DH Mishum): Above (302:9), I was stringent like those who say that soaking is Kivus even without filth. Here we are lenient, for Ze'iri explicitly permitted this and all the Poskim bring this.
Shulchan Aruch (319:16): One may drink wormy water through a cloth on Shabbos. Borer and sifting apply only when one fixes the food or drink before consuming it.
Magen Avraham (17): Those who hold that Libun applies even without filth would forbid through a cloth.
Mishnah Berurah (59): All permit for wine. Eliyahu Rabah says that all permit even water. In pressed circumstances, one may rely on this, since he does not intend for Libun.