סימן פ סעיף ד
אָסוּר לִתֵּן פְּרִי אוֹ מַיִם עַל הַתַּנּוּר לְאַחַר שֶׁהֻסַּק, מִשּׁוּם דְּאֶפְשָׁר שֶׁיַּרְתִּיחַ הַמַּיִם וְשֶׁיִּצָלֶה הַפְּרִי. וַאֲפִלּוּ אֵין דַּעְתּוֹ אֶלָּא לְחַמֵּם אוֹתָם קְצָת, מִכָּל מָקוֹם אִם בַּמָּקוֹם הַזֶּה אֶפְשָׁר שֶׁיִּתְבַּשְּׁלוּ אוֹ יִצָּלוּ, אָסוּר לְחַמְּמָן שָׁם. וְכֵן פַּשְׁטִידָה שֶׁיֵּשׁ בָּהּ שֻׁמָּן אֵין לְהַעֲמִידָהּ נֶגֶד הַמְּדוּרָה אוֹ עַל הַתַּנּוּר בְּמָקוֹם שֶׁתּוּכַל לְהַרְתִּיחַ, אַף עַל פִּי שֶׁאֵין דַּעְתּוֹ אֶלָּא לְחַמְּמָהּ. אֲבָל בְּמָקוֹם שֶׁאִי אֶפְשָׁר שֶׁיִּתְבַּשְּׁלוּ אֶלָּא יִתְחַמְּמוּ קְצָת שָׁם, מֻתָּר לִתְּנָם, וַאֲפִלּוּ נִקְרַשׁ הַשֻּׁמָּן אוֹ הַמַּיִם מֵחֲמַת הַקֹּר. אֲבָל לְתוֹךְ הַתַּנּוּר שֶׁהִטְמִינוּ בּוֹ, אָסוּר לָתֵת שׁוּם דָּבָר צוֹנֵןשֶׁיִּתְחַמֵּם, אַף עַל פִּי שֶׁאִי אֶפְשָׁר לְהַרְתִּיחַ שָׁם. וּלְצֹרֶךְ קְצָת חוֹלֶה, יַעֲשֶׂה שְׁאֵלַת חָכָם (עַיֵן נִשְׁמַת אָדָם) (רנ"ג רנ"ט שי"ח ש"כ). וּקְצָת נוֹהֲגִין לְהַחֲזִיר בַּשַׁבָּת הַמַּאֲכָלִים לְתוֹךְ הַתַּנּוּר שֶׁהִטְמִינוּ בּוֹ, כֵּיוָן שֶׁהֵם עֲדַיִן חַמִּים. אַךְ אִם נִצְטַנְּנוּ לְגַמְרֵי, אוֹסְרִים. וּבַעַל נֶפֶשׁ יֵשׁ לוֹ לְהַחְמִיר בְּכָל עִנְיָן.
It is forbidden to place fruit or water on a hot stove because the water might boil and the fruit might bake.22I.e. you might forget to remove them before they are cooked or roasted. Even if your intention is only to warm them a little, nevertheless, if on this place it is possible that they will boil or bake, it is forbidden to warm them there.23If you did it already and removed it before it attained the heat of yad soledes, you may probably use it. (Tehilah LeDavid 318: 29) Likewise, pudding (kugel) containing fat should not be placed near a fire or on an oven in a place where it may boil, even if you intend only to warm it. But in a place where it cannot be cooked but only warmed somewhat, you are permitted to place it,24According to Magen Avraham 259: 12, even to place it on an oven in a place where it cannot reach yad soledes, nevertheless requires a separation (like a blech) between the pot and the oven. On Erev Shabbos, you may place it in such a spot without a separation [Shulchan Aruch Harav]. The Magen Avraham may be referring only to food not thoroughly cooked. (Tehila LeDovid 253) even if the fat is congealed25This is in accordance with Shulchan Aruch 318: 16 and Ramban etc. Even though you may not crush ice to make ice water, because you would be changing it from a solid to a liquid [changing a form is called nolad, creating], in this instance you are not actually doing it, rather it happens by itself (from the warmth) [Mishnah Berurah 318: 102]. The Rema says our custom is to be machmir [stringent] unless it is very necessary for you to do it. The Shaarei Teshuva 318: 7—says there are no grounds to be machmir in this if it is not yad soledes. This is probably the intention of the Kitzur Shulchan Aruch. or the water is frozen. But in an oven in which food is kept warm, it is forbidden to put anything cold for the purpose of warming, even if it cannot boil there. If it is needed for one who is slightly ill, a halachic authority should be consulted. There are some who are accustomed to replace foods into the oven on Shabbos where they had been kept warm, since they are still warm. But if they cooled off completely, it is forbidden to do so. A spiritually sensitive person should be stringent in all such cases.
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)