Rif Shabbat 23b

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23b

{Shabbat 51a}
and they may be removed on the Sabbath -- and we conclude in it that it is indeed a refutation. Therefore, he need not stick it in and then remove it, but only to reveal part of it -- and so is the halacha.

"A CRUSE MAY BE FILLED {WITH [COLD] WATER AND PLACED UNDER A PILLOW OR BOLSTER}":
Rav Yehuda cited Shmuel: Cold [water, food, etc.] is permitted to be hidden.

Rav Nachman said to his servant Daru: Put away cold water for me, and bring me water heated by a Gentile cook.
Rav Ami heard of this and was upset at this.
Rav Yosef said: Why should be have been upset? He {Rav Nachman} acted in accordance with his teachers, one [act] being according to Rav, and the other according to Shmuel. According to Shmuel, for {in our gemara Rav Yehuda cited Shmuel} Shmuel said: Cold [water, etc.] may be hidden {insulated}.
According to Rav, for Rav Shmuel son of Rav Tzadok {our gemara: Yitzchak} cited Rav: Whatever can be eaten in its natural state, raw, is not subject to [the interdict against] the cooking of Gentiles.
But he [R. Ammi] held that an important man is different {and should be more stringent with himself}.

The Sages learnt {in a brayta}: Though it was said, One may not store [food] after nightfall even in a substance which does not add heat, yet if one comes to add {another covering}, he may add. How does he do it? Rabban Shimon ben Gamliel said: He may remove the sheets and replace them with blankets, or remove the blankets and replace them with sheets {depending on if he wants more or less insulation}. And thus did Rabban Shimon ben Gamliel say: Only the self-same boiler was forbidden {that is: food may not be insulated after nightfall in the same pot in which it was cooked}; but if it [the food] was emptied from that boiler into another, it is permitted.
If one stored {=insulated [food]} in and covered [it] with a substance that may be handled on the Sabbath, or if he stored [it] in something that may not be handled on the Sabbath, but covered [it] with something that may be handled on the Sabbath, he may remove [the covering] and return it.
If one stored [food] in and covered [it] with a substance that may not be handled on the Sabbath, or if he stored (it] in something that may be handled on the Sabbath, but covered it with something that may not be handled on the Sabbath, provided it was partly uncovered, he may take it [out] and replace [it], but if not,

{Shabbat 51b}
it may not be removed and replaced.
Rabbi Yehuda says: Thoroughly beaten flax is the same as foliage.
{that is, it adds heat, and therefore food may not be put away in it even before the Sabbath}
A boiler may be placed upon a boiler, and a pot upon a pot, {a boiler is of copper, and a pot is of earthenware}, but not a pot upon a boiler, or a boiler upon a pot. And the mouth [thereof] {Rabenu Chananel: of the lower vessel} may [also] be daubed over with dough: not in order to make them {the contents of the upper vessel} hotter, but that [their heat] may be retained.
And just as hot [food] may not be hidden, so may cold [food] not be hidden.
Rabbi permitted cold [food] to be hidden.
And neither snow nor hail may be broken up on the Sabbath in order that the water should flow, but they may be placed in a goblet or dish, without fear {of desecrating Shabbat, even though the melt}.

END PEREK FOUR