Shabbat 47B

אבל אסור. ולא יתקע, ואם תקע ⁠— חייב חטאת. רבן שמעון בן גמליאל אומר: אם היה רפוי ⁠— מותר.

However, doing so is prohibited. And one may not fasten the pieces together forcefully, and if he fastens them, he is liable to bring a sin-offering for performing a labor prohibited by Torah law. Rabban Shimon ben Gamliel says: If it was loose and could be assembled with ease, it is permitted. R' Abba and Rav Huna bar Ḥiyya relied on this opinion.

בי רב חמא הוה מטה גללניתא. הוה מהדרי לה ביומא טבא. אמר ליה ההוא מדרבנן לרבא: מאי דעתיך ⁠— בנין מן הצד הוא? נהי דאיסורא דאורייתא ליכא, איסורא דרבנן מיהא איכא! אמר ליה: אנא כרבן שמעון בן גמליאל סבירא לי דאמר אם היה רפוי ⁠— מותר.

The Talmud relates: In the house of Rav Ḥama, Rava’s grandfather, there was a collapsible bed, similar to a weaver’s loom, and they would reassemble it on a Festival. One of the rabbis said to Rava: What is your opinion? Do you hold that this is allowed because it is building in an atypical manner? In other words, one is not performing the prohibited labor of building since it is was not performed in the standard manner? Although there is no Torah prohibition, there is, in any case, a rabbinic prohibition. Rava said to him: I hold in accordance with the opinion of Rabban Shimon ben Gamliel who said that if it were loose, it is permitted even ab initio.

מתני׳ נותנין כלי תחת הנר לקבל ניצוצות, ולא יתן לתוכו מים מפני שהוא מכבה.

Mishnah: One may place a vessel beneath the oil lamp in order to receive burning sparks of oil that fall from the lamp so that they will not cause a fire. And he may not place water into the vessel because he thereby extinguishes the sparks.

גמ׳ והא קמבטל כלי מהיכנו! אמר רב הונא בריה דרב יהושע: ניצוצות אין בהן ממש.

Talmud: The Talmud asks: How is it permitted to position this vessel to receive the sparks, doesn’t he thereby negate the vessel’s preparedness? It is no longer prepared for any use on Shabbat as the sparks accord it set-aside status. The opinion that negating the preparedness of a vessel is prohibited has already been stated. Rav Huna, son of Rav Yehoshua, said: Sparks have no substance. They burn immediately and do not leave behind any trace of oil in the vessel. Therefore, the vessel remains suitable to be moved.