אורח חיים רע״הOrach Chayim 275

Se’if 1א׳

אֵין פּוֹלִין (פי' לְבַעֵר אֶת הַכֵּנִים מֵהַבְּגָדִים, תַּרְגּוּם בִּעַרְתִּי הַקֹדֶשׁ (דְּבָרִים כו, יג) פַּלֵתִי), וְאֵין קוֹרִין בְּסֵפֶר לְאוֹר הַנֵּר וַאֲפִלּוּ אֵינוֹ מוֹצִיא בְּפִיו, שֶׁמָּא יַטֶּה. וְאֲפִלּוּ הוּא גָּבוֹהַּ עֶשֶׂר קוֹמוֹת שֶׁאֵינוֹ יָכוֹל לִגֹּעַ אֵלָיו, שֶׁלֹּא חִלְּקוּ חֲכָמִים בַּדָּבָר. וּמִטַּעַם זֶה יֵשׁ לֶאֱסֹר אֲפִלּוּ הוּא בַּעֲשָׁשִׁית אוֹ קָבוּעַ בְּחוֹר שֶׁבַּכֹּתֶל, וְכֵן בְּנֵר שֶׁל שַׁעֲוָה.

The Tasks Forbidden to Be Performed on Shabbos by the Glow of the [Shabbos] Lights, 12 Seifim: 1. One does not search [a garment] (The meaning [of "Pulin" is] to remove lice from clothing. The [Aramaic] translation of "biarti"is "paliti"[, coming from the same root as "Pulin"].) and one does not read in a book by the light of a candle, and even if he is not reading aloud, lest one tilts [the flame to make it more steady]. And [this applies] even he is ten stories high, where he cannot reach it [the candle], as the rabbis did not differentiate [between varying situations] in this matter. And for this reason, there is [room to extend this prohibition] even if the flame is enclosed in crystal, or set in an opening in a wall. And this applies to a wax candle as well.

Se’if 2ב׳

וְדַוְקָא אֶחָד, אֲבָל שְׁנַיִם קוֹרִים בְּיַחַד, שֶׁאִם בָּא הָאֶחָד לְהַטּוֹת (פי' לְהַטּוֹת הַנֵּר כְּדֵי שֶׁיַּגִּיעַ הַשֶּׁמֶן לַפְּתִילָה), יַזְכִּירֶנּוּ חֲבֵרוֹ. וְהוּא שֶׁקּוֹרִים בְּעִנְיָן אֶחָד, שֶׁאָז יַשְׁגִּיחַ הָאֶחָד בַּמֶּה שֶּׁיַּעֲשֶׂה חֲבֵרוֹ, אֲבָל בִּשְׁנֵי עִנְיָנִים לֹא. הַגָּה: וְיֵשׁ אוֹמְרִים דְּבִשְׁנֵי סְפָרִים, אֲפִלּוּ בְּעִנְיָן אֶחָד אָסוּר (בֵּית יוֹסֵף), וְלָכֵן אָסוּר לוֹמַר פִּיּוּטִים בְּלֵיל יוֹם טוֹב שֶׁחָל לִהְיוֹת בְּשַׁבָּת, בְּבֵית הַכְּנֶסֶת, וְכֵן נָהֲגוּ (מָרְדְּכַי וְסֵפֶר הַתְּרוּמָה וּסְמַ"ג וְהַגָּהוֹת).

2. Specifically, this prohibition was only issued with regard to an individual [reading] alone. Two people, by contrast, may read together because if one will attempt to tilt the lamp, the other person will remind him. [This leniency applies] only when they are reading the same subject matter; then, one pays attention to what the other is doing. But if they are reading two diffferent subject matters, no. RAMA: There are those who say that when they are reading from two different books, even if it the same subject, it is forbidden. [Beis Yosef]. And therefore it is forbidden to say piyutim in the synagogue at night on Yom Tov that falls on Shabbat, and this is our custom. [Mordechai; סה"ת; Sma"g; ]

Se’if 3ג׳

אִם יֵשׁ אַחֵר עִמּוֹ, אֲפִלּוּ אֵינוֹ קוֹרֵא, וְאוֹמֵר לוֹ: תֵּן דַּעְתְּךָ עָלַי שֶׁלֹּא אַטֶּה, מֻתָּר; וְהוּא הַדִּין אִם אוֹמֵר כֵּן לְאִשְׁתּוֹ.

3. If there is someone else with him, even if that person is not reading, and he says to him 'give me your attention so that I will not tilt (the candle) it is permitted. This is also the law if one says this to his wife.