Gemara

(Beraisa): "Dabru El Bnei Yisrael... Ki Yihyeh Zav" -- mid'Oraisa, Zivah (of a man or woman) applies only to Bnei Yisrael, but Chachamim decreed that Nochrim are like Zavim (or Zavos).

Chulin 106a (Rav Idi bar Avin): We wash before a meal of Chulin so that we will be used to guarding our hands from Tum'ah, lest we be Metamei Terumah. Also, it is a Mitzvah.

(Abaye): It is the Mitzvah to obey Chachamim.

(Rava): It is the Mitzvah to obey R. Elazar ben Arach, who derives it from "anyone whom a Zav will touch, and will not wash his hands."

(Rav Nachman): The verse cannot discuss one who touched a Zav. Washing his hands is not Metaher. He must immerse!

Rather, it teaches that someone else (not touched by a Zav, rather, he is about to eat. He) is Tamei until he washes his hands.

Yadayim 1:5 (Mishnah): Anyone may pour the water for Netilas Yadayim, even a Cheresh, lunatic, or child. One may put the barrel between his knees and wash.

One may tilt it on its side and wash. A monkey may pour the water;

R. Yosi disqualifies these two.

Rishonim

Tosfos (Nidah 71b DH Ma'areh): A Tosefta (Yadayim 1:7) teaches that anyone who is not Metamei the water through Masa (moving it), is Kosher for Netilas Yadayim. This implies that anyone who is Metamei the water through Masa is Pasul for Netilas Yadayim. Some derive that a Nochri may not pour the water. This is wrong. A Nidah or Yoledes washes her hands, even though she is Metamei the water! All the more so this applies nowadays, that we all wash with Tamei water. The Tosefta discusses Terumah, or Chulin Al Taharas Terumah.

R. Shimshon (Yadayim 1:5): Based on the Tosefta, a Nidah may not pour the water, and not a Nochri, for Chachamim decreed that they are like Zavim in every way. Even one who is Tamei Mes may not pour the water if the Kli is Mekabel Tum'ah, for it will be Metamei the water. It is clear from Mishnah 2:4 that Tamei water is Pasul for Netilas Yadayim. According to this, there is no solution nowadays. If a Nochri drew the water, it is Pasul. Even if a Tahor (Yisrael) drew it, we are all Tamei (Mes) and we touch the Kli and the water! Some explain that the Tosefta discusses only Terumah, but not Netilas Yadayim for Chulin. If not, how can a Nidah or Yoledes wash for themselves? They have Tum'as Masa! This is not a proper inference. We wash for Chulin so that (when Mashi'ach comes), we will be used to guarding the Taharah of hands for dealing with Terumah. If so, we do not distinguish Chulin from Terumah. Chachamim enacted Netilas Yadayim even for a Nidah, who may not eat Terumah, and the water on her hands is Tamei.

Rosh (Yadayim 1:5): Nowadays one may wash from a Nochri or Nidah, for in any case all the water is Tamei.

Hagahos Ashri (Berachos 2:11): Anyone may pour the water for Netilas Yadayim, even a Cheresh, lunatic, or a child about six or seven years old.

Poskim

Shulchan Aruch (OC 159:11): Anyone may pour the water for Netilas Yadayim, even a Cheresh, lunatic, child, Nochri or Nidah.

Beis Yosef (DH Aval): R. Shimshon (on the Mishnah) brings a Tosefta which says that if the pourer or Notel (the one who hands are washed), but not both, had intent, the first Tana is Metaher his hands, and R. Yosi is Metamei. R. Yosi requires intent of the pourer and Notel. It seems that he agrees about a Cheresh, lunatic or child, for they have intent. The Rashba rules like the first Tana. Perhaps R. Shimshon agrees, just he comes to resolve why a Stam Mishnah teaches that a Cheresh, lunatic or child may pour the water, and R. Yosi does not argue. Alternatively, even if the Halachah follows R. Yosi, perhaps this is only regarding eating Terumah.

Beis Yosef (DH u'Mah and DH v'Rabeinu ha'Gadol): The Mordechai says like Tosfos. Mahari Avuhav says that one Mefaresh brought R. Shimshon, but then gave another Perush of the Tosefta, that any Tamei who is Metamei an entire person if he touched him with his finger, i.e. Tum'os mid'Oraisa such as Tamei Mes and Bo'el Nidah, is Kosher for Netilas Yadayim. Any Tamei who is Metamei only the hands of a person he touches, i.e. Tum'os mid'Rabanan, may not pour the water. Chachamim made their enactment due to Terumah. People who eat Terumah separate from every Tum'ah mid'Oraisa, so Chachamim needed to decree only about Tum'os mid'Rabanan.

Beis Yosef (DH veha'Rosh): The Tur holds like the Rosh, who holds like Tosfos.

Beis Yosef (DH veha'Manhig): Ha'Manhig says that even a Cheresh, lunatic or child may pour the water, but not a Nochri or slave, for we require Ko'ach Adam, and they are not called Adam (Bava Metzi'a 114b). Orchos Chayim says that the Rambam says that a Nochri may not pour the water. It seems that this is a printing mistake, for the Rambam did not write so. However, Semag and Sefer ha'Terumah wrote like Tosfos and the Rosh, that a Nochri or Nidah may pour the water, and also the Rashba says so.

Taz (15): Nowadays a Nidah may pour, for in any case all the water is Tamei. The Maharshal says that even though we are lenient about water that a Nochri drew, for his Tum'ah is only mid'Rabanan, why should we be lenient about Nidah, which is Tum'ah mid'Oraisa? Maharam Matz said that he is careful not to wash from a Nochri, even though the Ri (in Tosfos) permitted and brought a proof from Nidos, who wash their hands even though they are Temei'os. One can reject the proof. There is no alternative for Nidos or Yoldos, or nowadays for all of us. We can be careful not to wash from a Nochri. The Maharshal concluded that fortunate is one who can be careful not to wash from water that a Nochri or Nidah drew, and all the more so not from water that they poured.

Magen Avraham (22): I say that one should be careful only if (the Nochri or Nidah) pours on his hands, but if they brought the water to the Kli, there is no problem.

Mishnah Berurah (69): Even though one may not wash through a Nochri or Nidah for Terumah, for they are Metamei the water through carrying it, Chachamim did not decree regarding washing for Chulin. Some say that it is because nowadays all the water is Tamei, for we are all Tamei Mes. The Acharonim wrote in any case l'Chatchilah it is good to be careful not to wash from them.

Kaf ha'Chayim (72): The Levush says that all of them are Kosher, for they all have Ko'ach Adam.

Kaf ha'Chayim (73): Ateres Zahav says that the Maharshal says that one should not wash from a Nidah, i.e. his daughter. One may not wash from his wife when she is Nidah, or from another man's wife even if she is Tehorah. Mishbetzos Zahav says that he teaches that other women should not wash from a Nidah.

Rema: Some say that a child below six is like a monkey.

Beis Yosef (DH Kuf): Tosfos, the Rosh and several Gedolim rule like R. Yosi, who disqualifies a monkey. Rav Yehudai (Gaon), the Rashba and Rambam rule like the first Tana, who is Machshir. It seems that Hagahos Ashri requires intent of the pourer, and a Cheresh and lunatic have intent, and also a six year old. Less than this he has no intent. He is like a monkey. However, I say that we rule like the first Tana (that even a monkey may pour).

Gra (v'Ika): This is because he has no Da'as, like it says in Gitin 59a about Pe'utos (mature children. Children become Pe'utos between six and 10, depending on their sharpness. They can buy and sell Metaltelim.) R. Yosi admits about a Cheresh, lunatic or child. Presumably, this is only if the child reached the age of Pe'utos, for then he has a little Da'as. Why is he unlike a lunatic, who cannot buy or sell even Metaltelim, like it says in Kesuvos 20a? Also, this is according to R. Yosi, but we hold like the first Tana, that the intent of the pourer or Notel suffices, and all the more so according to other Poskim who do not require any intent at all. Shechitah of a Cheresh, lunatic or child is Kosher, for we do not require intent, but a monkey is Pasul. We say in Chulin 12b that the actions of a minor count, and if his intent is evident through his action, he has intent mid'Rabanan. We can say that we discuss such a minor. The first Tana does not require this.

Mishnah Berurah (70): The Gra holds that one need not be stringent about a child above six. He is unlike a monkey, for a monkey is not Ko'ach Adam. Even though a child has no Da'as, he is not worse than a lunatic.

Kaf ha'Chayim (75): The Rema connotes that the Mechaber permits even below six. He connotes like this in the Beis Yosef. Shirei Keneses ha'Gedolah, Chesed la'Alafim and Ben Ish Chai are stringent like the Rema.

Shulchan Aruch (12): If a monkey pours the water, some disqualify, and some are Machshir. The latter opinion is primary.