If they [people] drink staining drinks on Shabbat, such as red wine or berry juice… they should be careful that they do not stain their cloths and sheets and clothing. A person who has cut his finger should be careful not to put anything on it, since it stains, for even though it is destructive and destructive acts are exempt [on a Torah level], there is a rabbinic prohibition.

(20) There is he who says that one who eats berries or other fruits that stain, must take care not to touch his stained hands to his clothing or a cloth, out of concern for tzovei’a.

Question: You asked if a person must be careful when he eats on Shabbat fruits that stain, such as berries and peaches and pomegranates, that he not wipe his hand with a cloth, since it is dyeing. And we have not seen anyone in our days who is careful with this, and it is certainly an excessive stringency, for this is not the manner of dyeing but the manner of dirtying…one need not be concerned, but one who is stringent merits a beracha.

There are those who are lenient with all of this, since it is done in a dirtying fashion, and one may rely on them where it is impossible to be careful about this.

Rather it is certain that a change in appearance [in an object] is not at all halachically significant when one does not want it at all, and it is also not the way of the world to want it at all. And that which it is prohibited to touch a cloth with his stained hands, this is because it is normal for cloth to be dyed, and if one were to do this not in the manner of dirtying, it would be a full-fledged melacha ….And know that otherwise it would be prohibited for a woman who became nidda on Shabbat to place any moch that she had prepared for nidda out of concern for dyeing…but there is no one who is concerned for it on account of dyeing….

She must immerse her whole body at once. Therefore, there must not be anything upon her that is a barrier [to the water].

For Rabbi Yitzchak said: As a matter of Torah [law], [something that covers] most of him, and he is particular about it, is a chatzitza [barrier], and that he isn’t particular about, is not a chatzitza. [The sages] decreed regarding [something that covers] most of him that he is not particular about…and [something that covers] a minority of him that he is particular about….Let them also decree regarding a minority that he is not particular about…This itself is a rabbinic decree, and we should arise and decree a decree atop a decree?

…even a minute [barrier], if people are normally particular about it sometimes, is a chatzitza even if she is not particular about it now. Or even if she is never particular about it, since most people are normally particular about it, it is a chatzitza. And if it covers most of the body, even if people are not normally particular about this, it is a chatzitza. Rema: And from the outset [le-chat’chila], she should not immerse even with things that are not a chatzitza, a decree on account of things that are a chatzitza.

Mar Ukva said: Discharge in the eye–moist is not a chatzitza; dry is a chatzitza. … Shemuel said: Kohl that is within the eye is not a chatzitza, and that is on the eye is a chatzitza. If her eyes are porchot, even on the eye it is not chatzitza.

Porchot: She opens and shuts [her eyes] frequently; either way [inside or outside the eye] it [kohl] is not a chatzitza, because her blinking moves [the kohl] so that it is not thick upon the eye and has no independent substance. A different language: They [the eyes] tear, for a tear moistens the kohl, and it is not a chatzitza.

…For all the things that are a chatzitza for immersion are a chatzitza for ritual handwashing…And so the things that a person is not particular about are not a chatzitza….If one was a painter and his hands were painted, the paint is not a chatzitza on his hand, even though the paints’ physical substance is on his hand. If he was not a painter, if his hands were painted and there was physical substance of the paint on his hands, this is a chatzitza, but wet it is not a chatzitza. And similarly, the women who normally paint their hands for beautification and the like, the color is not a chatzitza, neither for handwashing nor for immersion.

Dyes on women’s hands or on the hair for beautification, it seems to me that they are not a chatzitza because they [women] are never particular about them. On the contrary, they constantly go back and refresh them for beautification. Even though this dye spreads through all of the hair, and “[something that covers] most of him that he is not particular about” is a chatzitza [following the position that something covering a majority of the hair is a chatzitza], here she is particular that she wants it to be there, and this is as though it is part of the hair itself, and like a dyed cloth, for the dye is not like an additional thing that is a chatzitza, rather like the essence of the cloth and is not a chatzitza…and further it seems to me that there is no physical substance of the dye on the hair or on the hands but rather appearance of a color, and therefore it is not a chatzitza.

(18) And involving a woman: when a man has carnal relations with her, both shall bathe in water and remain impure until evening.

The Sages taught: The verse states: “And the woman, with whom a man shall lie giving seed, they shall both bathe themselves in water, and be unclean until the evening” (Leviticus 15:18). The extra term “with whom” comes to exclude a bride who does not become ritually impure; this is the statement of Rabbi Yehuda...Hon, son of Rav Naḥman, said to Rav Naḥman: Shall we say that Rabbi Yehuda holds: The Torah spared a bride’s adornments, including her make-up, and therefore exempted her from submersion in water, as that might cause them ruin?

A bride’s adornments – kohl and sarak [rouge] that she puts on her face and if she immerses, the water will remove them…

(24) There are those who have the practice not to eat meat on the day they go to the mikveh, since it gets in between the teeth more than other food. Even though they [women] check and clean the teeth, she is concerned lest some of it might remain of which she is unaware, and this is a good custom. Rema: And she should not eat between bathing and immersion (Rosh in the Laws of Nidda).

It is a good custom. And it is clear that if she did not do thus there is no need to delay the immersion for this, and on Shabbat and Yom Tov the custom is that they eat meat, she should just take care to clean very well afterwards.

If her husband is in town, it is a mitzva to immerse on time so as not to desist from procreation even one night. Rema: And she is permitted to immerse on Friday night (Rabbeinu Chananel and Rav Eliya and Or Zarua and Behag and Sefer Ha-Teruma and Semag in the name of Rav Shemuel who guided his daughter thus) if she cannot immerse beforehand…