Due to the restriction [against walking before washing], prior to going to sleep one is to prepare a basin of water near his bed to wash with upon awakening. [The water filled vessel is to be placed into an empty vessel into which one will pour the water into, as will be explained next.]
Is one to cover the Negel Vasser water at night prior to going to sleep?
Many opinions rule there is no need to be stringent against washing hands with water that was left revealed over night. This applies even in an area where snakes are commonly found. However there are opinions which are stringent and rule one is to avoid washing with revealed waters. Practically the custom is to be lenient completely even regarding drinking revealed waters, and certainly regarding using it for washing, and so is the apparent Chabad custom. There is likewise no problem to wash hands for bread using revealed waters even in areas that snakes are common.
May one place the Negel Vasser water under his bed?
One may not place food or liquid under a bed even if the food is covered with a metal vessel due to that an evil spirit dwells on it. Based on this ruling some Poskim question whether one may wash using water left under the bed. Other Poskim rule it is allowed. Practically one is to initially avoid doing so, although one who does so has upon whom to rely. One may certainly be lenient to place it under an airplane seat and the like.
Must the washing vessel be filled with water up to the very top?
A Maaseh Shehaya:
In the year 1962 Harav Asher Lemel Hakohen, current Rav of Anash Beitar Ilit, sat one Thursday night with a fellow student in the Beis Midrash in 770 discussing with him different personal issues. It came out in the conversation that the student does not prepare Negel Vasser at night with which to wash his hands with upon awakening. He stated various excuses for this practice, including fear that the water would spill and wet his clothing. That Shabbos during the Farbrengen with the Rebbe, of which both students participated, the Rebbe spoke about the saying of Modeh Ani and how there is no evil inclination that stops a person from reciting it. The Rebbe then suddenly interjected: “This is unlike the washing of hands in the morning, of which the evil inclination can tell someone that he should not prepare the water near his bed the night before due to fear of it spilling etc.” The Rebbe then continued with the original topic. Needless to say the student took upon himself to prepare Negel Vasser every night prior to going to sleep.
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 Seder Hayom; Elya Raba 1/4; Ketzos Hashulchan 2/1; Chelkas Yaakov 3/152
 Seder Hayom states: “Every G-d fearing Jew needs to prepare for himself prior to going to sleep two vessels, one that contains water and one that is empty, into which he will pour the water upon awakening.”
 Seder Hayom ibid; The filled vessel is blessed while the empty vessel is cursed.
 See Hakashrus p. 432; Piskeiy Teshuvos 4/12
 Shalmei Tzibur brought in Shaareiy Teshuvah 4/7; Pischeiy Teshuvah Yoreh Deah 116/1; So is also implied from M”B 160/23; Peri Toar Yoreh Deah 116/2; Birkeiy Yosef 116/4; Admur 272/1 rules we are no longer careful regarding revealed waters as snakes are no longer commonly found.
 Shalmei Tzibur ibid, as the stringency of not drinking from revealed waters in areas with snakes only applies to drinking and not washing. [Shaareiy Teshuvah ibid; M”B 160/23]
 Rav Sheptal brought in Shaareiy Teshuva ibid; Seder Hayom: “Every G-d fearing Jew needs to prepare for himself prior to going to sleep two vessels, one that contains water and one that is empty, into which he will pour the water upon awakening. One is to place the water filled vessel into the empty vessel, covered and clean.”; Chesed Lealafim 4/10
 Conclusion of Shaareiy Teshuvah ibid
 See Migdal Oz story 114 from which it is proven that it was not an acceptable Chabad custom to cover the waters. This is seen from the fact the apprentice of the Tzemach Tzedek could not understand why he covered the water, as well as from the fact one Chassid complained to the Rebbe Rashab about the stringencies of another Chassid who followed this ruling of covering the water. Nevertheless, as is evident from the story, this was the custom of the Tzemach Tzedek. However from his response it is understood that this custom is not meant as a directive for the public.
 M”B 160/23. It is implied from there that he rules even regarding washing hands upon awakening there is no need to be stringent.
 Admur in Shemiras Hanefesh Vehaguf Halacha 7.
 Piskeiy Teshuvah 1
 Sheivet Halevy 8/22; Shraga Hameir 7/72; See also Kaf Hachaim Yoreh Deah 116/43-44 that the prohibition only applies to an earth floor
 Halichos Shlomo 20 footnote 49 in name of Rav SZ”A, and so seems from Sheivet Halevy ibid
 Regarding eating foods or liquids that have been left under one’s bed it is said that Rav SZ”A ruled to forbid it even Bedieved, and so ruled also Rav Aba Shaul. However many Poskim permit it. [Shvus Yaakov, brought in Pischeiy Teshuvah 116; Chayeh Adam [2/2]; Rav Akiva Eiger; Yad Efrayim; Arugas Bosem; Kaf Hachaim Yoreh Deah 116/44.] Sefer Hakashrus [p. 435] rules that the Poskim rule that Bedieved it is allowed, especially in a case of loss, although when applicable, one is to wash the food three times.
 Hakashrus p. 436 based on Kaf Hachaim ibid
 In the Siddur Admur writes that one is to take “a vessel filled with water” It requires analysis as to the novelty of this statement. Does it mean that the vessel should be filled to its top even if it holds much more than a Revius? See Seder Netilas Yadayim 1
 Shabbos Mevarchim Chodesh Shvat
 Printed in Hisvadyos 5722 [Vol. 32] p. 362