Rif Brachot 41a

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41a

{digression to Chullin 106a.}

when they were valid {before they were heated.}

Water which became unfit for an animal to drink, in vessels they are not valid {for hand washing}, but in the ground they are valid {to immerse one's hands within}.
By way of explanation, some say this means water so salty that a dog is unable to lap from them, and some say this means muddy water that is almost like thin clay {which can be poured from vessel to vessel}.

Rav Iddi bar Avin cited Rav Yitzcahk Asiyan: the only reason we wash hands for chullin {unconsecrated food} is because of fear of ruining teruma. {Hands can become sheni, and invalidate teruma, and they applied this general practice of washing hands to chullin as well}, and furthermore because of mitzvah {commandment}.
What mitzvah?
Abaye said: that it is a mitzvah to listen to the words of the Sages.
and Rava said: it is a mitzvah to listen to the words of Rabbi Eleazar ben Arach.

[From here the Sages said that washing the hands is from the Torah.]

Rabbi Oshaya said: Anything that you dip in liquids, you need to wash your hands.

Rabbi Eleazar and Rabbi Oshaya said: They only said washing of the hands for fruits because of cleanliness.

And this statement argues with that of Rav Nachman. For Rav Nachman said: one who washes his hands for fruit is of the haughty of spirit.

Rabba bar bar Chana said: One time I stood before Rabbi Ami and Rabbi Assi, and they brought before them a basket of fruit. They ate and did not wash their hands {beforehand}, and they did not offer me from it, and each one blesses {afterwards} to himself. And we may deduce from this three things. We may deduce that there is no washing of hands for fruit. And we deduce that two who have eaten, it is a mitzvah to separate. And we deduce that there is no zimmun for fruits.

{Chullin 106b}
The Sages learnt {in a brayta}:
Kiddush of the hands {and feet, from the kiyor} in the Temple was until the {upper} joint {that is, the connection between the hand and the arm}. In chullin until the joint {the joint in the middle of the fingers}. In teruma, until the joint {at the gav hayad}.