The Mishna in Shabbat relates that one day, when Beit Shammai outnumbered Beit Hillel in the court, they locked the doors and enacted eighteen different decrees. Among these was the decree that touching items with one’s hands renders those items impure unless one washes his hands first. The Gemara explains that the reason for the enactment is “yadayim askaniyot hein,” meaning that when left to their own devices, hands will wander and touch things that they are not supposed to touch. This same principle appears in the Mishna in Taharot as well, which says that one (i.e., a kohen) who is pure and becomes distracted in the middle of eating teruma must treat his hands as impure due to yadayim askaniyot hein. What is this principle, and how does it explain the halachic obligation to wash hands at various times?
The Rishonim differ as to the actual meaning of this phrase. Rabbeinu Chananel, the Rambam, and the Ritva all understand that yadayim askaniyot hein relates to tuma, or impurity. When one ceases to pay attention to what one’s hands are touching, explains the Rambam, one is liable to touch items that are impure. Were one then to eat teruma (or kodshim, sacrificial food, for that matter) in such a state, one would render the teruma inedible due to impurity. To prevent this, Chazal decreed that one should always treat one’s hands as impure and as capable of rendering teruma impure. To remove this impurity (which is rabbinic in nature), one can wash hands, rendering them pure as long as one remains focused on an action that requires purity of hands (such as eating teruma). However, when one removes his focus from such an action, the hands automatically revert to their default impure status.
Rashi, in contrast to these Rishonim, understands that the concern of yadayim askaniyot hein refers to issues of actual cleanliness. Rashi does not understand why it would relate to impurity, as if that were the case, it is not logical that only one’s hands would be impure. Furthermore, it would not make sense that hand washing alone would suffice. If impurity were the real issue, one would need to immerse in a mikveh! Instead, Rashi understands that Chazal were concerned that one would eat teruma with dirty hands, thereby rendering the teruma repulsive and causing one not to eat it. To avoid this, they enacted the decree of washing hands before eating teruma. As an aside, the Ritva (who does interpret the concern to be of ritual impurity rather than uncleanliness) responds to these questions of Rashi, writing that Chazal, who enacted the decree of impurity of the hands, also devised the enactment to wash one’s hands prior to eating teruma as a reminder that one’s hands should not come in contact with impurity. They therefore also had the right to decide not to be overly stringent and to suffice with washing of the hands alone.
We can understand the logic behind both sides of this dispute in the Rishonim as far as eating teruma is concerned. But do the same approaches make sense within other cases of washing hands in halacha, such as when eating non-teruma foods?
The Gemara in Pesachim writes that one needs to wash hands twice on the Seder night, a practice with which we are familiar. But why twice? After all, we already washed once for the karpas! The answer given is that one will lose focus on one’s hands throughout the telling of the story of leaving Egypt and the accompanying Hallel, which leads to concern that one’s hands may be unclean. This, indeed, is how the Rambam explains the issue.
At first glance, this seems to be another application of the principle of yadayim askaniyot hein, and this is indeed how Rav Kapach understands the Rambam’s opinion. There is, though, a problem with this approach. Why is one considered to have lost focus on his hands during the reading of the Haggada? Rav Kapach himself asks this question and defines “losing focus” by comparing washing hands to tefillin, where one must remain focused on the tefillin while wearing them. The problem with this comparison is that concerning tefillin, one has no obligation to actively think about the tefillin. Rather, one must make sure that one acts appropriately with tefillin on, and only inappropriate lightheartedness is off limits. If the same guidelines concerning tefillin hold true for one’s hands, then where is there any inappropriate lightheartedness at the Pesach Seder? We are involved in a mitzva of telling the story of leaving Egypt, so this seemingly would not involve losing one’s focus!
There is another way of understanding the underlying principle here, which can be better understood by carefully studying another case – losing focus during a meal. If one goes to the restroom in the middle of a meal, must he wash his hands again afterwards?
The Shulchan Aruch writes, based upon a responsa of the Ramban, that if one loses focus on one’s hands during a meal and touches one of the concealed areas of the body, he must wash his hands again and recite a beracha. Indeed, the Pri Megadim understands this case as a nafka mina (practical difference) between the Rambam and Rashi (in the machloket mentioned above), where the Rambam posits that the decree to wash hands is due to impurity, while Rashi says it is due to uncleanliness. Thus, Rashi would hold that washing is required with a beracha (as the Shulchan Aruch rules) because one touched unclean areas of the body while relieving oneself, while the Rambam would hold washing with a beracha is not required because one was careful not to touch any impure objects. Upon closer inspection, however, things do not seem to add up.
The Bi’ur Halacha points out that according to the Pri Megadim, the Shulchan Aruch is following a ruling of the Ramban without noting anywhere that many Rishonim, including Rambam, disagree. The Bi’ur Halacha consequently suggests that the ruling of the Shulchan Aruch is based upon an entirely different matter altogether. The key to unlocking this mystery lies in understanding a surprising comment of Rabbeinu Chananel and in understanding why we wash hands before eating bread in the first place.
We saw above that Rabbeinu Chananel understands the principle of yadayim askaniyot hein and the consequence of being obligated to wash hands when taking one’s mind off of them as a function of purity and impurity. It is all the more surprising, then, that concerning the Gemara in Pesachim discussing washing twice on Seder night, Rabbeinu Chananel writes that the reason is due to cleanliness! It is important to note here that Rabbeinu Chananel is often a key primary source upon which the Rambam based his halachic decisions, and it is therefore critical for understanding the Rambam’s position on this point as well.
The Gemara in Masechet Chullin discusses the reasoning for needing to wash one’s hands for non-consecrated food. There, two answers are given – either because of serach teruma or because Chazal made a decree to do so (no other reason than that is given). The Bi’ur Halacha suggests that Rabbeinu Chananel (and by extension the Rambam) may not think that hand washing for eating chullin bread is connected to teruma at all. Therefore, this halacha of washing one’s hands again after using the restroom during a meal would be applicable according to all opinions.
There is good reason to think that the Rambam would agree with this assessment. Rav Nachum Rabinovitch, zt”l points out that the halachot of hand washing concerning chullin do not perfectly match those of teruma. Concerning teruma, for example, one must wash one’s hands twice – once to remove the initial impurity and once to remove the water so the hands do not become impure again. When washing for chullin, washing twice is unnecessary. Additionally, one need not wash for chullin fruit, a practice we would expect to be necessary if washing for chullin was due to “serach teruma.” Rav Rabinovitch writes that perhaps the most significant support to his contention is the Rambam’s glaring omission in Hilchot Berachot 6:1 of any reason for washing one’s hands for chullin.
Instead, Rav Rabinovitch understands that the Rambam views the need to wash hands for chullin as an extension of the mitzva not to eat things that are disgusting. Rav Rabinovitch quotes the Rambam elsewhere who writes in a manner reminiscent of Rashi’s opinion above: “They made it forbidden to eat with dirty hands, or on dirty dishes, as these are all included in the prohibition of “do not be disgusting.” According to this assessment, there is ample room to understand that the Rambam would agree with the ruling of the Shulchan Aruch that one should wash one’s hands after going to the bathroom during a meal. This would also explain the need to wash during the Pesach Seder, as we are concerned that one’s hands touched an unclean item during that time.
There is, however, another way of understanding the Rambam’s approach. Even if we accept Rav Rabinovitch’s explanation concerning the disconnect between the decree to wash hands for chullin and washing hands for teruma, this still does not require us to say that the Rambam holds like Rashi. Instead, we can posit that the Rambam looks at the decree of washing as a unit in and of itself.
In this paradigm, one would have to wash for a meal because Chazal said so and for no other reason – meaning that once that requirement has been fulfilled (once per meal), then it would no longer be necessary to wash again, no matter what occurs to one’s hands. According to this, yadayim askaniyot hein is a general rule that requires hand washing, but it is not explanatory in the sense of requiring a further hand washing during a meal.
One problem with this explanation is the issue of Seder night. If the halacha that one must wash hands for a food that will be dipped (דבר שטיבולו במשקה) is because of the general chullin hand washing decree, why is it necessary to wash again because of distraction? One potential answer to this would be to point to the language of the Mishna in Taharot: “When one decides he is done eating, even though he knows that his hands have not become impure, his hands become impure.” If we accept that the halachot of hand washing run along the same general lines throughout halacha (with some minor alterations, as we saw above), we can explain that the same is true at the Seder. Once someone decides that they have eaten enough karpas and begin the main part of the Seder (where they probably will not be eating, although this is not explicitly forbidden in the Rambam), they would be beginning a new act of eating when they get to motzi matza and would therefore have to wash again.
To summarize, there are four general approaches we can take to explain the roots of hand washing for chullin. The first is to posit that it is connected completely to the laws of teruma, and that the original decree to wash hands for teruma is also because of impurity – this is the approach of Rav Kapach within the Rambam. The second approach agrees that the halachot of teruma and chullin are identical, but posits they are both because of cleanliness – this is the opinion of Rashi. The third approach is to explain that the halachot are different. The requirement to wash hands for teruma is because of purity and impurity (in accordance with the Rambam), whereas washing hands for chullin is because of cleanliness (like Rashi) – this is the opinion of Rav Rabinovitch. The fourth and final way to explain the basis for washing hands is that concerning teruma, it is because of impurity (like the Rambam) and for chullin, it is a special decree, with no reason given.
 Shabbat 14a
 She’ar Avot HaTuma 8:8, 13:3; Perush HaMishnayot, Zavim 5:12
 Chiddushim, Shabbat 14a
 Chametz Umatza 8:1,6
 Ibid., 6
 Berachot 6:18
 O.C. 164:2
 O.C., Introduction to the laws of hand washing
 164:2, s.v. “לחזור וליטול”
 See ״עיונים במשנתו של הרמב״ם״ by Rav Nachum Eliezer Rabinovitch, p.15:
״מתוך כך נתברר עד כמה שקועים פירושיו של רבינו חננאל ז״ל בהלכות רי״ף ז״ל, והרבה סתמות של רבינו, בין בפירוש המשנה ובין בספר היד, החצבו מתורתו של הר״ח ז״ל״
 Yad HaPeshuta, Introduction to Berachot 6, 6:1-2
 Ma’achalot Assurot 17:29-30.