Beitzah 31
ביצה ל״א — ד"ה גְּמָ׳ וְהָאָמְרַתְּ רֵישָׁא אֵין מְבַקְּעִין כְּלָל
Beitzah 31:2
Shmuel permits untying, unraveling, and cutting fastenings on vessels on both Shabbat and Yom Tov since the prohibition against dismantling does not apply to vessels, but a baraita objects by permitting unraveling and cutting such fastenings only on Yom Tov and not on Shabbat.
אָמַר שְׁמוּאֵל: חוֹתָמוֹת שֶׁבַּקַּרְקַע — מַתִּיר, אֲבָל לֹא מַפְקִיעַ וְלֹא חוֹתֵךְ. שֶׁבַּכֵּלִים — מַתִּיר וּמַפְקִיעַ וְחוֹתֵךְ, אֶחָד שַׁבָּת וְאֶחָד יוֹם טוֹב. מֵיתִיבִי: חוֹתָמוֹת שֶׁבַּקַּרְקַע, בְּשַׁבָּת — מַתִּיר אֲבָל לֹא מַפְקִיעַ וְלֹא חוֹתֵךְ. בְּיוֹם טוֹב — מַתִּיר וּמַפְקִיעַ וְחוֹתֵךְ!
Shmuel said: In the case of fastenings made of knotted ropes that are attached to the ground and that serve as closures for doors of cellars and caves, one may untie the knot, but one may not unravel the rope itself into its constituent fibers nor cut the rope. This constitutes the prohibited labor of dismantling the cellar or cave on Shabbat. With regard to fastenings that are on the doors of vessels, e.g., cupboards, it is permitted to untie, or unravel, or cut them if necessary, both on Shabbat and on a Festival, as the prohibition against dismantling does not apply to vessels. The Gemara raises an objection to this from the following baraita: In a case of fastenings that are attached to the ground, which are on doors, on Shabbat one may untie the rope but not unravel or cut it. Although it is permitted to do so by Torah law, the Sages prohibited it. However, on a Festival, one may untie or unravel or cut it, as this is not prohibited even by rabbinic law. This appears to contradict the opinion of Shmuel, who does not differentiate between Shabbat and Festivals.

