Mishnayos Sukkah Perek 2 Mishnah 1

One who sleeps beneath the bed in the sukka did not fulfill his obligation, because the bed constitutes a tent that serves as a barrier between him and the roofing of the sukka. Rabbi Yehuda said: It was our custom that we would sleep beneath the bed before the Elders and they did not say anything to us to the effect that we are not fulfilling our obligation. Apparently, the halakhic status of the bed is not like that of a tent and it does not prevent fulfillment of the mitzva. § Rabbi Shimon said, contrary to the opinion of Rabbi Yehuda: There was an incident involving Tavi, the Canaanite slave of Rabban Gamliel, who was sleeping beneath the bed, and Rabban Gamliel lightheartedly said to the Elders: Did you see my slave Tavi, who is a Torah scholar and knows that slaves are exempt from the mitzva of sukka? Since it is a positive, time-bound mitzva, Canaanite slaves, whose status with regard to this halakhic category is like that of women, are exempt from the obligation to fulfill the mitzva of sukka. Therefore, he sleeps under the bed. Rabbi Shimon continued: And by the way, as Rabban Gamliel was not issuing a halakhic ruling, we learned that one who sleeps beneath the bed did not fulfill his obligation.

הַיָּשֵׁן תַּחַת הַמִּטָּה בַסֻּכָּה, לֹא יָצָא יְדֵי חוֹבָתוֹ. אָמַר רַבִּי יְהוּדָה, נוֹהֲגִין הָיִינוּ, שֶׁהָיִינוּ יְשֵׁנִים תַּחַת הַמִּטָּה בִּפְנֵי הַזְּקֵנִים, וְלֹא אָמְרוּ לָנוּ דָבָר. אָמַר רַבִּי שִׁמְעוֹן, מַעֲשֶׂה בְטָבִי עַבְדּוֹ שֶׁל רַבָּן גַּמְלִיאֵל שֶׁהָיָה יָשֵׁן תַּחַת הַמִּטָּה, וְאָמַר לָהֶן רַבָּן גַּמְלִיאֵל לַזְּקֵנִים, רְאִיתֶם טָבִי עַבְדִּי, שֶׁהוּא תַלְמִיד חָכָם וְיוֹדֵעַ שֶׁעֲבָדִים פְּטוּרִין מִן הַסֻּכָּה, לְפִיכָךְ יָשֵׁן הוּא תַּחַת הַמִּטָּה. וּלְפִי דַרְכֵּנוּ לָמַדְנוּ, שֶׁהַיָּשֵׁן תַּחַת הַמִּטָּה, לֹא יָצָא יְדֵי חוֹבָתוֹ: