- תחילתו וסופן בשגגה
The final Mishnah in the perek states that if one threw an object and then remembered it was Shabbos after it left his hand but before it landed, and another person caught it, or a case where a dog caught it, or if it got burned before it landed, he is patur from bringing a chatas. Similarly, if one threw an object with the intent to injure a person or an animal (which he would then be liable for causing a bruise on Shabbos) and then remembered it was Shabbos after it left his hand, he is patur. The Mishnah concludes with a klal, that, כל חייבי חטאות אינן חייבין עד שתהא תחלתן וסופן בשגגה, - All who are liable for a chatas, are not liable unless the beginning and the completion of their action was done beshogegg.
- Two amos beshogeggg, then bemeizid, then beshogeggg
There is a machlokes Amoraim in a case where one transports an object two amos beshogegg, two amos bemeizid and then two amos beshogegg. Rabbah says he is patur whereas Rava says he is chayav.
-Rabbah says he is patur, and even according to Rabban Gamliel who holds אין ידיעה לחצי שיעור – there is no awareness for a half measure, and therefore two half measures combine to make one chayav, this principle only applies in a case where one wrote one letter beshogegg, became aware of his sin, and then wrote a second letter beshogegg. Since the second letter was also written beshogegg, Rabban Gamliel holds he is liable. In our case though, the person is completing the four amos bemeizid, and therefore, he is not liable for a chatas.
-Rava says the case is where the person threw the object, and even the Rabbonim who hold of יש ידיעה לחצי שיעור, would say he is liable. In the case of the writing, the writer was in control in choosing to write the second letter. Therefore, his forgetting that it’s Shabbos renders the writing a separate act, and the two writings do not combine to make him chayav. Here, however, in the case of throwing the object, he is no longer in control of retrieving the object, and therefore the entire transfer is regarded as one act beshogegg.
- Building is chayav even for a כל שהוא
The opening Mishna in the perek of Haboneh, states that one is liable for the melacha of boneh (building) if he builds even a minimal amount.
The Gemara asks what practical use is building a minimal amount, and after rejecting two answers, concludes with the opinion of Rav Acha bar Yaakov who said that someone with a large home who has a hole in the wall, will seal it with clay. A similar thing was done in the construction of the Mishkan when a craftsman would pour molten lead into a small hole in a beam, that a worm had bored.
