Gemara

Sleep is a 60th of death.

Shabbos 109a (Beraisa - R. Noson): The Ru'ach that dwells on hands before washing is a Bas Chorin (dignified). It does not go away unless each hand is washed three times.

Sukah 26b (Rav): One may not sleep during the day more than a horse's sleep.

This is 60 Nishmi (breaths).

Abaye: My Rebbi (Rabah) sleeps like Rav, who slept like Rebbi, who slept like David, who slept like a horse, i.e. 60 Nishmi.

Abaye used to sleep [during the day] the amount of time needed to go from Bei Kuvi to Pumbedisa. Rav Yosef applied to him "Ad Masai Atzel Tishkav Masai Takum mi'Shenasecha."

Kidushin 70b (Rav Yosef): Everyone in Bei Kuvi of Pumbedisa is a slave.

Rishonim

Rashi (Sukah 26b DH Lishon): One may not sleep more than 60 Nishmi due to Bitul Torah.

Rashi (Sukah 26b DH k'Me'ayel): Elsewhere, we find that this distance (from Bei Kuvi to Pumbedisa) is six Parsa'os.

Question: Where do we find this? Rashi (Kidushin 70b) says that Bei Kuvi is a village near Pumbedisa! Also Kesuvos 111a and Gitin connote like this.

Answer (Noda bi'Yehudah 2 OC 20): Rashi did not say that a Gemara says so. Perhaps a Medrash says that the distance is six Parsa'os. Kidushin 70b proves that there is another place called Bei Kuvi. Rav Yosef needed to specify the Bei Kuvi near Pumbedisa.

Note: If so, why does the Gemara say 'from Bei Kuvi to Pumbedisa' to specify a time or distance, without specifying which Bei Kuvi it discusses? Especially since there is a Bei Kuvi near Pumbedisa, people are prone to think that it refers to that one!

Aruch l'Ner (26b DH k'Me'ayel): In Gitin 4a, Rashi himself connotes that it is less than six Parsa'os! He explains that on the borders of Eretz Yisrael there are protrusions four or five Parsa'os, and cities are enveloped within them. Rabah bar bar Chanah says that from Kefar Ludim (an enveloped city) to Lud is like from Bei Kuvi to Pumbedisa. I.e. it is at most four or five Parsa'os. Here, Rashi says that it is six! Also, a person walks 10 Parsa'os in a day. It is difficult to say that Abaye used to sleep the majority of the day. It seems that there is a printing mistake in Rashi here.

Note: The "proof" that it is at most four or five Parsa'os assumes that Lud was the closest part of Eretz Yisrael to Kefar Ludim. Why can't we say that it was six Parsa'os away, and it was the closest city, but indeed Kefar Ludim was within four or five Parsa'os of the border?

Sha'arei Teshuvah (OC 4:17): Tif'eres Tzvi (1) wants to correct the text [of Rashi] to say two Parsa'os. Also for this, there is no source. In Gitin 4a, Rashi connotes that it is at most four or five Parsa'os. Based on Sukah 26b, we must say that four or five is not precise.

Poskim

Shulchan Aruch (OC 4:14): If one rose before dawn and washed his hands, it is not unclear whether or not he must wash again after dawn to remove the Ru'ach Ra'ah on the hands.

Rema: He washes without a Berachah.

Beis Yosef (DH v'Im): If one rose early to learn and washed his hands, and later lied down to sleep before day (dawn), since the Ru'ach Ra'ah went away once through washing three times, it does not rest on the hands again that night. Or, perhaps it returns. The Zohar connotes like this. It says that David ha'Melech would not sleep past 60 Nishmi, for after this, one tastes death and the Ru'ach ha'Tum'ah rules over him. It does not distinguish whether or not he slept earlier that night.

Mishnah Berurah (31): Some say that the Ru'ach Ra'ah returns at dawn.

Shulchan Aruch (15): If one sleeps during the day, it is not unclear whether or not he must wash three times. He should wash without a Berachah.

Beis Yosef (DH u'Lefi): Perhaps even one who sleeps during the day must wash, for it says Stam that when one sleeps 60 Nishmi, Ru'ach ha'Tum'ah rules over him. It did not distinguish between day and night. The Zohar says that anyone who sleeps at night tastes death, but perhaps this is also during the day. It merely discusses what is normal, that people sleep at night. It also discusses sleeping on a bed. Surely it does not depend on this! The Tum'ah is because the Neshamah leaves, and the Ru'ach ha'Tum'ah dwells there. This is even if he sleeps not on a bed. Likewise, it does not depend on night. This is why Sukah 26b forbids sleeping more than 60 breaths during the day. However, perhaps the Tum'ah is only for sleeping at night, for this is the time of the Tum'ah. It has no power during the day to rule over man. The Isur to sleep more than 60 breaths during the day is lest one arouse the Sitra during the day, which is not its time. Still, perhaps even if it is aroused through sleep, it has no power to dwell on a person. This requires investigation. Later, I found that Orchos Chayim says that if one rose before dawn and washed his hands, some say that he must wash again after dawn, because Bas Melech (a powerful Tum'ah) dwells on the hands the entire night until the day. This is why one must pour water on them three times. He connotes that even if one was awake until morning ,he must wash again due to Bas Melech.

Taz (11): There is a Safek whether Ru'ach ha'Tum'ah is due to night, or due to sleeping.

Magen Avraham (14): This is only if he slept 60 Nishmi.

Gra (DH Yashan): Orchos Chayim holds that one need not wash. Also the Zohar connotes like this, but perhaps it does not depend on night, and it merely discusses the usual case; really it depends on sleep. Sukah 26b connotes like this. It forbids sleeping 60 Nishmi even during the day for this reason.

Sha'arei Teshuvah (17): Tif'eres Tzvi says that 60 Nishmi does not vary between Shabbos and weekdays. The Ari Zal used to sleep two or three hours [on Shabbos day]. This implies that three hours is not more than 60 Nishmi. It is Midas Chasidus not to sleep more than three hours during the day. This is why Rav Yosef applied to Abaye "when will you rise?" He must hold that Shabbos is better [for sleeping] than other days. Since sleep on Shabbos is Ta'anug (a delight), there is no Midas Chasidus not to sleep more than two hours [during the day on Shabbos]. However, perhaps we cannot derive the Shi'ur of 60 Nishmi from what he brought about the Ari Zal. Perhaps the Ari Zal woke up several times during the two or three hours he slept, and never slept 60 Nishmi at once. The Birkei Yosef (Machazik Berachah, Kuntres Acharon) said 'I heard from a Chacham who was a long time on the road, and he counted many times the sleep of horse. He counted 59 breaths, and the horse awoke. This was more than a half hour. However, Alfasi Zuta of the Rama mi'Pi'ano says one breath is one part in 1080 of an hour (slightly more than three seconds). If so, 60 Nishmi is only one part in 18 of an hour, i.e. three and a third minutes. Sukah 26b, and the Tur and Shulchan Aruch (OC 231) connote unlike this. The Birkei Yosef brings from R. Chaim Vital that Ru'ach Ra'ah dwells on one who sleeps during the day.

Kaf ha'Chayim (58): Some say that 60 Nishmi is about half an hour. Some say that it is three and a third minutes.

Mishnah Berurah (34): Ru'ach Ra'ah does not dwell on one who sleeps less than 60 Nishmi, even at night.

Kaf ha'Chayim (59): Divrei Shalom (48) says that there is no Ru'ach Ra'ah during the day. He countered the Birkei Yosef's proofs from R. Chaim Vital that there is Ru'ach Ra'ah. Emes l'Yakov agreed with Divrei Shalom, but concluded that one should wash without a Berachah, and so says the Ben Ish Chai.

Shulchan Aruch (16): David was careful not to sleep 60 Nishmin, in order not to taste death.

Magen Avraham (15): Emek ha'Melech says that on Shabbos one should sleep during the day.

Bi'ur Halachah (DH David): Some learn from the Ari Zal that 60 Nishmi is three hours. Some say that we cannot learn from a Chacham on Shabbos. Also, perhaps he woke several times in the middle, and never slept 60 Nishmi. Some say that it is more than a half hour. Some say that it is a little more than three minutes. A Ba'al Nefesh should be stringent according to his ability.

Kaf ha'Chayim (57): If one was awake until midnight, and then said Berachos and Tikun Chatzos, even if he sleeps afterwards, there is no problem. (He does not taste death.)

Kaf ha'Chayim (58): During the week, sleep is usually bad for Tzadikim. On Shabbos, no harm will come from it. One can gain from it! It is proper to sleep after the meal. This is why the Ari Zal slept two or three hours after the meal.

Rema: The Gemara connotes that only during the day he was careful.

Beis Yosef (DH v'Im): David dozed like a horse. The Zohar says that the secret of this is 'David ha'Melech lives forever.' Sleep is a 60th part of death. David was always careful not to doze for more than 59 breaths, for past this, one tastes death, and the Ru'ach of Tum'ah rules over him.' This shows that whenever one sleeps 60 breaths, he must wash.

Magen Avraham (16): This is difficult. Sukah 26b says so only about the Amora'im. David was careful even at night, like the Beis Yosef brings from the Zohar. Berachos 3a says that until midnight, David slept like a horse, i.e. 60 Nishmi at a time. The harp would wake him if he was amidst the 60 Nishmi. The Rema was bothered why the Beis Yosef taught that David was careful. It must be that a Ba'al Nefesh (pious person) should be stringent, like it says in Sukah, but only during the day.

Mishnah Berurah (36): A Ba'al Nefesh should be careful not to sleep 60 Nishmi during the day. This does not apply to Shabbos. If one cannot learn from without sleeping a little in the afternoon, he may do so, but he should not sleep too much. He sleeps to serve Hash-m, and not for pleasure.