יורה דעה קצ״הYoreh De'ah 195

Se’if 1א׳

חַיָּב אָדָם לִפְרֹשׁ מֵאִשְׁתּוֹ בִּימֵי טֻמְאָתָהּ עַד שֶׁתִּסְפֹּר וְתִטְבֹּל. וַאֲפִלּוּ שָׁהֲתָה זְמַן אָרֹךְ וְלֹא טָבְלָה, תָּמִיד הִיא בְּנִדָּתָהּ עַד שֶׁתִּטְבֹּל (בֵּית יוֹסֵף בְּשֵׁם הַפּוֹסְקִים). וְלֹא יִשְׂחֹק וְלא יָקֵל רֹאשׁ עִמָּהּ אֲפִלּוּ בִּדְבָרִים (טוּר וּבֵית יוֹסֵף בְּשֵׁם רַשְׁבָּ"א מֵאָבוֹת דְּר"ן) שֶׁמָּא יַרְגִּיל לַעֲבֵרָה; אֲבָל מֻתָּר לְהִתְיַחֵד עִמָּהּ, דְּכֵיוָן שֶׁבָּא עָלֶיהָ פַּעַם אַחַת תּוּ לֹא תַּקִּיף יִצְרֵיהּ (ל' עַצְמוֹ).

Matters that are prohibited during her time of menstruation, including 17 paragraphs: A person is obligated to separate from his wife during the days of her impurity until she counts and immerses (even if she waits a long time to immerse). She is always in her Niddah status until she immerses (Beis Yosef in the name of halakhic authorities). He should not joke or engage in levity with her (even with words) (Tur and Beis Yosef in the name of the Rashba from Avot d'Rabbi Nasan) lest he become accustomed to sin. However, he is permitted to be alone with her since once he has had intercourse with her one time, his urger will no longer overcome him (his own language).

Se’if 2ב׳

לֹא יִגַּע בָּהּ אֲפִלּוּ בְּאֶצְבַּע קְטַנָּה, וְלֹא יוֹשִׁיט מִיָּדוֹ לְיָדָהּ שׁוּם דָּבָר וְלֹא יְקַבְּלֶנּוּ מִיָּדָהּ, שֶׁמָּא יִגַּע בִּבְשָׂרָהּ. וְכֵן עַל יְדֵי זְרִיקָה מִיָּדוֹ לְיָדָהּ אוֹ לְהֶפֶךְ, אָסוּר. (בִּנְיָמִין זְאֵב ס"ס קנ"ט וְהַגָּהוֹת ש"ד בְּשֵׁם המהר"ם).

He may not touch her, even with his little finger, nor may he pass anything from his hand to her hand, nor may he accept from her hand, lest he touch her flesh (similarly, by throwing from his hand to hers or vice versa, is also prohibited).

Se’if 3ג׳

לֹא יֹאכַל עִמָּהּ עַל הַשֻּׁלְחָן, אֶלָּא אִם כֵּן יֵשׁ שׁוּם שִׁנּוּי שֶׁיִּהְיֶה שׁוּם דָּבָר מַפְסִיק בֵּין קְעָרָה שֶׁלּוֹ לַקְּעָרָה שֶׁלָּהּ, לֶחֶם אוֹ קַנְקַן, אוֹ שֶׁיֹּאכַל כָּל אֶחָד בַּמַּפָּה שֶׁלּוֹ. הַגָּה: וְיֵשׁ אוֹמְרִים הָא דִּצְרִיכִין הֶפְסֵק בֵּין קְעָרָה שֶׁלּוֹ לַקְּעָרָה שֶׁלָּהּ הַיְנוּ דַּוְקָא כְּשֶׁאֵינָן אוֹכְלִין בִּקְעָרָה אַחַת כְּשֶׁהִיא טְהוֹרָה, אֲבָל אִם אוֹכְלִין בִּקְעָרָה אַחַת כְּשֶׁהִיא טְהוֹרָה סָגֵי אִם אוֹכֶלֶת בִּקְעָרָה בִּפְנֵי עַצְמָהּ, וְאֵין צָרִיךְ הֶכֵּר אַחֵר, (הַגָּהוֹת אֲשֵׁרִי בְּשֵׁם ר"י וְהַגָּהוֹת אַלְפָסִי), וְכֵן נוֹהֲגִין. יֵשׁ אוֹמְרִים שֶׁאָסוּר לוֹ לֶאֱכֹל מִשִּׁיּוּרֵי מַאֲכָל שֶׁלָּהּ, (מְצָא בְּקוּנְטְרֵס דְּהִלְכוֹת נִדָּה), כְּמוֹ שֶׁאָסוּר לִשְׁתּוֹת מִשִּׁיּוּרֵי כּוֹס שֶׁלָּהּ, וּכְמוֹ שֶׁיִּתְבָּאֵר.

He may not eat with her at the table unless there is some difference, that there is something separating between his plate and her plate, bread or a pitcher, or that each one eats on their own tablecloth. Rama: There are those who say that the requirement of separation between his plate and her plate is specifically when they don't eat from the same plate when she is pure. However if they normally eat from a single plate when she is pure, it suffices if she eats from her own plate, and they don't need another reminder (Hagahot Ashiri in the name of R"i and Hagahot Alfasi) and this is the practice. There are those who say that it is prohibited for him to eat what remains on her plate (found in a commentary on the laws of Niddah) just as it is prohibited for him to drink what remains in her cup, as will be be explained.