בבא דרישא פטור ומותר לא קתני אלא בבא דסיפא דפטור אבל אסור קשיא
the first section of the mishna speaks of cases in which the one performing the actions is exempt from punishment by Torah law, and even by rabbinic law he is ab initio permitted to perform those actions. When the poor person or homeowner neither lifted nor placed the object, i. e., the object was placed into or removed from their hands by others, their role is insignificant. Therefore, it was not taught in the mishna, and those cases were not factored into the total number of acts of carrying from domain to domain. However, with regard to the latter section of the mishna, where the person performing those actions is exempt by Torah law, but his actions are prohibited by rabbinic law, it is difficult. Since the Sages prohibited those actions, they should be included in the total in the mishna, which should be twelve, not eight.
Incidentally, the Gemara wonders: Is there, in all the halakhot of Shabbat, an act for which the mishna deems one exempt and the act is permitted? Didn’t Shmuel say: With regard to all exempt rulings in the halakhot of Shabbat, although one who performs the action is exempt by Torah law, his action is prohibited by rabbinic law. This applies to all cases except for these three cases for which one is exempt and he is permitted to perform the action: Trapping a deer, where he does not actually trap it, rather he sits in the entrance of a house that a deer had previously entered on its own, preventing its exit; and trapping a poisonous snake because of the danger that it poses; and one who drains an abscess, meaning one who lances the boil of pus and drains the liquid from it. If so, the cases in the first section of our mishna, where the ruling is exempt, must be understood as exempt but prohibited.
כי איצטריך ליה לשמואל פטורי דקא עביד מעשה פטורי דלא קא עביד מעשה איכא טובא
The Gemara answers: In these cases, too, the ruling is: Exempt and permitted. When, though, was it necessary for Shmuel to cite specific cases as exempt and permitted? It was necessary in exempt cases where he performs a defined action. However, there are many exempt cases where he does not perform an action, which are completely permitted.
מכל מקום תרתי סרי הויין פטורי דאתי בהו לידי חיוב חטאת קא חשיב דלא אתי בהו לידי חיוב חטאת לא קא חשיב
The Gemara returns to Rav Mattana’s question: In any case, there are twelve actions that should have been enumerated in the mishna. The Gemara answers: The mishna took into consideration cases of exempt acts where the one who performed them could come, through their performance, to incur liability to bring a sin-offering. The mishna did not take into consideration cases of exempt acts where the one who performed them could not come, through their performance, to incur liability to bring a sin-offering. Here, only the instances where one lifts an object from its place are taken into consideration. Having lifted an object, if he continued, he could potentially incur liability to bring a sin-offering. Under no circumstances can one who merely places an object come to violate a more serious prohibition.
שניהן פטורין והא אתעבידא מלאכה מבינייהו תניא רבי אומר מעם הארץ בעשותה העושה את כולה ולא העושה את מקצתה יחיד ועשה אותה חייב שנים ועשו אותה פטורין איתמר נמי אמר רבי חייא בר גמדא נזרקה מפי חבורה ואמרו בעשתה יחיד שעשאה חייב שנים שעשאוה פטורין:
The Gemara asks about the mishna itself: In the latter section of the mishna, instances in which they are both exempt are enumerated. However, wasn’t a prohibited labor performed between the two of them? Since together they performed an act prohibited by a severe Torah prohibition, how is it possible that their partnership will result in both being exempt? The Gemara answers that it was taught in a baraita that Rabbi Yehuda HaNasi said: It is written: “ And if one soul sins unwittingly from the people of the land when he does it, one of the laws of God that should not be done and he is responsible” (Leviticus 4:27). The verse’s emphasis on the words“ when he does it” means: One who does all of it, i. e., the entire transgression, is liable and not one who does part of it. Therefore, an individual, and he performed an action in its entirety, is liable. However, two people, and they performed an action together, are not liable, as each one performed only part of the action. The Gemara comments: It was also stated in support of Rabbi Yehuda HaNasi’s opinion: Rabbi Ḥiyya bar Gamda said: Amidst a discussion of these matters, it emanated from the group of Sages and they said: From the verse’s emphasis on“ when he does it” it is derived: An individual who performed it is liable. However, two who performed it are not liable.
Rav raised a dilemma before Rabbi Yehuda HaNasi: One whom another person loaded with food and drink on his back in the private domain on Shabbat, and he carried them out while they were still on his back, what is the halakha with regard to the prohibition of carrying out on Shabbat? Clearly, one who lifts an object with his hand in the private domain, and carries it out into the public domain is liable, as he performed the complete act of carrying out. However, in the case of one who is laden with an object; is moving his body from its place in the private domain considered like lifting the object itself from its place? In that case, he would be liable. Or, perhaps it is not considered like lifting the object from its place, and therefore he would not be liable. Rabbi Yehuda HaNasi said to him: He is liable, and it is not similar to the halakha of one who had an object placed in his hand and carried it out to the public domain, with regard to which we learned in the mishna that he is not liable by Torah law. What is the reason for the distinction between these two apparently similar cases? His body is at rest, in a defined place. However, his hand is not at rest. Since a hand is not generally fixed in one place, moving it and even transferring it to a different domain without a bona fide act of lifting is not considered lifting. However, the body is generally fixed in one place. Moving it from its place is considered lifting in terms of Shabbat, and he is liable for doing so.