Shabbat 92B

ואם תמצא לומר אנשי הוצל עושין כן ⁠— בטלה דעתן אצל כל אדם.

And if you say that the people of Hotzal do so and therefore they should be liable, their intention is rendered irrelevant by the opinions of all other people.

מתני׳ המתכוין להוציא לפניו, ובא לו לאחריו ⁠— פטור. לאחריו ובא לו לפניו ⁠— חייב. באמת אמרו: האשה החוגרת בסינר, בין מלפניה ובין מלאחריה ⁠— חייבת, שכן ראוי להיות חוזר. רבי יהודה אומר: אף מקבלי פתקין.

Mishnah: One who intends to carry out an object with the object before him, and as he was walking the object came to be carried behind him, is exempt. However, if he intended to carry it out behind him and it came to be carried before him, he is liable. In truth they said: A woman who girded herself in a pants-like sinar worn beneath the outer garments, whether she placed an object before her or behind her, and it came to be carried on the other side, she is liable, as it is common for the sinar to be reversed. R' Yehuda says: Even those royal couriers, who receive notes [pittakin], carry those notes in their belts, and are not particular where on their belt they carry the notes (Rav Hai Gaon), are liable for carrying out the notes whether they carried them before them or behind them.

גמ׳ מאי שנא לפניו ובא לו לאחריו דפטור ⁠— דלא אתעבידא מחשבתו, לאחריו ובא לו לפניו נמי, הא לא אתעבידא מחשבתו! אמר רבי אלעזר: תברה, מי ששנה זו לא שנה זו. אמר רבא: ומאי קושיא? דילמא: לפניו ובא לו לאחריו היינו טעמא דפטור ⁠— דנתכוון לשמירה מעולה ועלתה בידו שמירה פחותה, לאחריו ובא לו לפניו היינו טעמא דחייב ⁠— דנתכוון לשמירה פחותה ועלתה בידו שמירה מעולה.

Talmud: The Talmud asks: What is different about the case of one who intended to carry an object before him and it came to be carried behind him that he is exempt? The reason is that his intention was not realized. Since he did not perform the act that he intended to perform, he is exempt. If so, then even in the case of one who intended to carry an object behind him, and it came to be carried before him, he should also be exempt because his intention was not realized. R' Elazar said: This Mishnah is disjointed, in the sense that it cites the opinions of two different rabbis. He who taught this halakha did not teach that halakha. Rava said: And what difficulty is there here? Perhaps it can be explained as follows. With regard to one who intended to carry an object before him, and it came to be carried behind him, this is the reason that he is exempt: He intended to provide the object with outstanding protection, seeing it at all times, and ultimately he managed to provide the object with reduced protection. Since that was not his intention, it is not considered a prohibited labor and he is exempt. Whereas one who intended to carry an object behind him, and it came to be carried before him, this is the reason he is liable: He intended to provide the object with reduced protection, and ultimately he managed to provide the object with outstanding protection.