Beitzah 33B

אוכלי בהמה ⁠— אין בהן משום תקון כלי.

Animal fodder, such as straw and reed branches, does not have any associated prohibition due to the preparing of a vessel. One may therefore trim it on Shabbat and use it as one wishes.

איתיביה רב כהנא לרב יהודה: מטלטלין עצי בשמים להריח בהן, ולהניף בהן לחולה, ומוללו ומריח בו. ולא יקטמנו להריח בו, ואם קטמו ⁠— פטור אבל אסור. לחצוץ בו שיניו ⁠— לא יקטמנו, ואם קטמו ⁠— חייב חטאת!

Rav Kahana raised an objection to Rav Yehuda from the following baraita: One may handle wood of a spice tree on Shabbat in order to smell them and to wave them before a sick person to fan him. And he may crush it between his fingers to release its fragrance, and he may smell it. However, he may not cut it from the branch in order to produce a moist spot on the branch that will emit a strong fragrance, so as to smell it; and if he did cut it, he is exempt from punishment according to Torah law, but it is prohibited to do so. If he intends to clean his teeth with it, he may not cut it, and if he did cut it, he is liable to bring a sin-offering for transgressing a prohibited labor on Shabbat. This indicates that although some wood of a spice tree was used as animal fodder, it is nevertheless prohibited to cut it. This appears to contradict Rav Yehuda.

אמר ליה: השתא פטור אבל אסור קא קשיא לי, חייב חטאת מבעיא? אלא: כי תניא ההיא בקשין. קשין בני מלילה נינהו?

Rav Yehuda said to Rav Kahana: Now, even the statement exempt but prohibited poses a difficulty to my opinion, and it is not reasonable. Is it required to say the opposite, i.e., liable to bring a sin-offering? This teaching cannot be understood at face value; rather, it must be understood as follows: When that baraita was taught, it was referring to hard pieces of wood such as beams, with regard to which there is a concern that one might perform a prohibited labor. The Talmud questions this: And can hard branches be crushed by hand?