Gemara

(Mishnah): If a wife brought four slaves into the marriage, she sits in a comfortable chair (and need not work at all).

61a (Rav Yitzchak bar Chananya): Nevertheless, she mixes his drink, sets his bed, and washes his hands, feet and face.

(Rav Yitzchak bar Chananya): A Nidah does for a husband everything that a wife does, except for these three Melachos.

(Rava): Setting the bed is forbidden only in front of him.

Shmuel's wife would serve his drink unnaturally, with her left hand. Abaye's wife would place it on top of a barrel. Rava's wife would place it at the head of his bed. Rav Papa's wife would place it on a bench.

Shabbos 13a (Tana d'vei Eliyahu): A widow was complaining 'it says "Ki Hi Orech Yamecha." My husband learned and served Chachamim, yet he died young!'

Eliyahu: How did he act with you when you were Nidah?

The widow: He didn't even touch my pinky!

Eliyahu: How did he act with you during the days of Libun? (Nowadays, Bnos Yisrael count seven clean days after any sighting of blood.)

The widow: He would eat and drink with me, and we slept in the same bed without clothes, but he never even considered relations!

Eliyahu: Blessed is Hash-m who killed him, and did not show partiality (to overlook his Mezid transgression) due to his Torah!

Rishonim

Rif and Rosh (5:24): A Nidah does for a husband everything that a wife does, except for mixing his drink, setting his bed, and washing his hands, feet and face. Setting the bed is forbidden only in front of him. Shmuel's wife would serve his drink unnaturally, with her left hand. The wives of Abaye, Rava and Rav Papa would place it on top of a barrel, at the head of his bed, and on a bench, respectively.

Ran (DH Chutz): These three Melachos entail closeness and affection. We forbid pouring the water on him. It cannot mean washing him with her hands, for in any case she may not touch him.

Rosh (ibid., citing R. Shemayah): Rashi was careful not to take a key from his wife's hand when she was Nidah. We cannot learn from the Amora'im who did not take a drink from their wives' hands, for that shows affection. We learn from Eliyahu Rabah that other things are permitted. Eliyahu asked the widow if her husband passed to her a flask or oil and touched her. She said only that he didn't touch her.

Rebuttal (Rosh, ibid.): The Gemara does not discuss serving a drink, rather, mixing it. All are careful not to pass any object from hand to hand. Eliyahu wanted the widow to admit that her husband passed things to her, which will surely lead to touching. He should have been stringent, like everyone else. She said that he relied on his great zealousness to avoid touching her. This shows that it is forbidden for others.

Ran (ibid.): The Yerushalmi forbids a Kalah (she observes the stringencies of Nidah due to Dam Besulim) to pass a cup to her husband all seven days. This implies that other Kelim are permitted. The Rambam agrees.

Beis Yosef (YD 195 DH Kol): SMaG suggests that perhaps oil shows affection. In any case one who is stringent will be blessed.

Rosh and Ran (ibid.): Rashi and R. Chananel say that the Amora'im's wives served them drinks unnaturally during the days of Libun. R. Tam says that one may not be more lenient during the days of Libun than during the first seven days of Nidah. Eliyahu asked the widow about the days of Libun because he knew that the Talmid erred and was improperly lenient. It is difficult to say that he erred about this. Rather, women used to immerse after the seven days of Nidah mid'Oraisa, for the sake of Taharos, and then fulfilled R. Zeira's stringency to count seven clean days and immerse again. Nowadays, women immerse only after the seven clean days, so they are full Nidos mid'Oraisa until then.

Rambam (Hilchos Ishus 21:8): A Nidah does for a husband everything that a wife does, except for mixing his drink, setting his bed, and washing his hands, feet and face. This is a decree due to thoughts, lest he come to have relations with her. Therefore, she may set his bed in his absence, and may mix his drink but does not put it in his hand like usual. Rather, she puts it on the ground, a Keli or the table, and he takes it.

Magid Mishneh: The Rambam forbids passing a cup. He permits other things.

Ramach: The Rambam should have distinguished like the Rif, that during the days of Libun she may pass anything except for a cup, but during the days of Nidah she may not pass anything!

Rambam (Hilchos Isurei Bi'ah 11:19): A Nidah may not wash her husband's hands, feet and face, mix his drink, or set his bed in front of him. This is a decree lest they sin.

Magid Mishneh: Rav Hai Gaon forbids sleeping on her bed even when she is not there. This is reasonable, for it is more prone to lead to sin than making his bed in front of him.

Hagahos Maimoniyos (50): The Re'em requires a Shinuy only if she mixes the drink and serves it to him. It seems that we are concerned only for mixing with water, not for pouring from the Keli, like we do. However, to do so on the table requires a Shinuy. Setting the bed refers to sheets. Pillows and blankets are permitted.

Question (Ramach): Why did the Rambam omit the Heter through a Shinuy? Why did he omit our custom not to pass things? Rashi (an early version, brought in Shitah Mekubetzes DH v'Zeh Leshon Rashi) permits passing anything except for a cup.

Answer (Beis Yosef 195 DH Aval): Perhaps the Rambam holds that a Shinuy helps only for one with great Yir'as Shomayim who will not come to sin. It does not help for common people.

Poskim

Shulchan Aruch (YD 195:10): A Nidah does everything for her husband, except for mixing his drink (Rema - in front of him) and setting it on the table in front of him, unless there is some reminder (that she is forbidden). E.g. she puts it on the table with her left hand, or on a pillow or blanket even with her right hand.

Beis Yosef (DH Kosav): The Magid Mishneh says 'only wine is forbidden. Water is permitted.' The inferences contradict each other regarding other drinks. The Rashba permits everything except for wine. It is best to say that the Magid Mishneh agrees.

Beis Yosef (DH Nir'eh): Setting his bed shows great affection, yet it is permitted in his absence. All the more so she may mix his drink in his absence! The Mordechai agrees.

Bach (DH Motzasi): Maharash forbids a Nidah to bring bowls (of food) to the table, just like mixing his drink. However, the Re'em permits, for he requires a Shinuy only if she mixes the drink and serves it to him. The Rashba forbids only when she mixes wine with water. And even if bringing a bowl is like mixing a drink, it is forbidden only if it is specifically for him. Therefore, it is proper to be careful only in this case, which shows affection. There is no concern for bowls for the entire family, for then there is no affection.

Shach (13): It seems that the Bach is stringent for other drinks.

Shulchan Aruch (11): She may not set his bed in front of him. This refers to sheets, which is affectionate. Setting the pillows and blankets is exertion, not affectionate. It is permitted. Everything is permitted in his absence, even if he knows that washing she is setting them.

Beis Yosef (DH u'Mah she'Chosav Afilu): The Rashba says that whatever is not in front of him will not lead to sin.

Shulchan Aruch (12): She may not pour water for him to wash his hands, feet and face, even if without touching him, even if the water is cold.

Beis Yosef (DH v'Asurah): The Rashba forbids even if he washes and she pours. To touch is forbidden in any case. Even cold water is forbidden. And in Sefer ha'Yir'ah it says (Our text of the Beis Yosef ends like this.)

Chidushei Hagahos (6): It should say 'Sefer ha'Yir'ah forbids bringing a flask of water and Kelim for him to wash his feet, for this shows affection. (Shach (16) also cites this from R. Yonah (Igeres ha'Teshuvah 75).)

Rebuttal (Drishah 4 and Taz 8): Some say that throwing to him or pouring on him is always forbidden (even without the affection of washing), and here we forbid filling the Kelim from which he will wash. This is wrong. The Rashba implies that she may prepare the water for him, just she may not pour on him. If preparing water was forbidden, we should have forbidden bringing water for washing. Perhaps later generations adopted the stringency not to throw things, even not for washing.