Resources for Kesubos daf 30
1. The גמרא says that according to ר׳ ישבב the difference between שמעון התמני and רבי שמעון בן מנסיא is בעולה לכהן גדול, where according to שמעון התמני there is הויה so he is חייב קנס but according to רבי שמעון בן מנסיא he is פּטור since its not ראויה לקיימה. רבי עקיבא איגר brings a question from his son in law which he doesn’t have an answer to: why don’t we say that there is no קנס according to all since there really is no הויה to this woman since we have principle called אי עביד לא מהני which means that if the תורה says not to do something then it isn’t חל. If so, since the תורה said that the כהן גדול cannot be with this woman then the קידושין won’t be חל and there won’t be הויה. The סוכת דוד in אות י"ב has an interesting חקירה to address this question: what creates the "לא מהני"? Is it a special side הלכה to not let it be חל or is it the איסור itself that stops it from being חל. If you say it is a side הלכה then one could answer רע"א’s question by saying that she is בעצם a woman who has הויה and its just a side reason that stops her from marriage. However, if the איסור itself is what blocks the חלות then רע"א’s question would still stand since the איסור itself makes it that there is no הויה.
2. The גמרא brings the ברייתא of רבי נחוניא בן הקנה that someone who is חייב כרת is פּטור from תשלומין. The רבנן in our משנה who argue with him hold that we only say קים ליה בדרבה מיניה by a case of חייבי מיתות ב"ד. There is a critical רש"י in בבא מציעא דף צ"א ע"א ד"ה רבא אמר where רש"י says that קם ליה בדרבה מיניה is only a פּטור from ב"ד, since ב"ד cant enforce two punishments on a person. However, the person is still חייב to pay בדיני שמים. The צל"ח in פּסחים דף כ"ט ע"א ד"ה רבי נחוניא learns from this an incredible חידוש. He says that there are really two מחלוקתים between the רבנן and רנבה"ק. One מחלוקת is whether we apply קלב"מ by cases of חיובי כרת or not. The other מחלוקת is whether there is a חיוב תשלומין בידי שמים, because רש"י sounds like the issue is that ב"ד has a limitation that it can’t be מחייב a person two punishments since there is a דרשה of רשעה אחת אתה מחייבו ולא שתי רשעיות. However, כרת is not a punishment given out by ב"ד which is why according to the רבנן the ב"ד can enforce it. However, according to רנבה"ק who says קלב"מ applies even to חיובי כרת, it must be that even בית דין של מעלה can only give out one חיוב and not two. If so, you are פּטור from paying the person even בדיני שמים. The אחיעזר in א׳ סימן כ׳ אות ח disagrees and says that even according to רנבה"ק the mandate of רשעה אחת ולא שתי רשעיות was said to ב"ד של מטה. However, the lomdus of רשעה אחת ולא שתי רשעיות is that when there is one רשעה, even if that רשעה comes from a חיוב בשמיםof כרת, ב"ד can’t enforce the second רשעה of paying money, but there still is a חיוב בדיני שמים.
Similar to the צל"ח mentioned above, there is a מהרש"ל quoted by the קצות inסימן כ"ח ס"ק א that says in a case of קם ליה בדרבה מיניה if the person who was damaged just grabbed the money from the מזיק he can keep it since קלב"מ is just a limitation on ב"ד ability to enforce the payment but if the person took it they can keep it since there is a חיוב בידי שמים to pay. The מהרש"ל is מחדש further, as the קצות explains him, that this only applies if the person didn’t actually get the חמור punishment such as מיתה. However, if they actually got the חמור punishment then the חיוב בידי שמים would not exist. The קובץ שיעורים here explains that the מהרש"ל understands that getting the more חמור עונש is considered to include the smaller עונש (בכלל מאתים מנה). Therefore, if someone actually got the bigger עונש then they don’t need to pay.