Menachos Daf 54 מנחוס דַף 54

Rebbe Ill’a said: אין לך הקשה לקמיצה יותר ממנחת חוטא – you have no minchah which is more difficult to perform kemitzah than the sinner’s minchah, because no oil is added, and some of the dry flour will likely fall away when the Kohen brushes the kometz. Rav Yitzchak bar Avdimi said that one can knead a מנחת חוטא with water, which eases the kemitzah. The Gemara suggests that the latter opinion holds כמות שהן משערינן – we assess the flour’s volume as it is now, so adding water will not deviate from the correct volume, and Rebbe Ill’a holds לכמות שהיו משערינן – we assess the flour’s volume based on what it was originally, so one may not add water, which will alter the required volume of flour. However, the Gemara concludes that all may agree we assess its volume as it is now. Rav Yitzchak bar Avdimi holds that the Torah’s term "חריבה" – dry only means חריבה משמן – dry from oil, but water may be added, and Rebbe Ill’a holds it means חריבה מכל דבר – dry from any [liquid], and even water may not be added.

A Mishnah states: בשר העגל שנתפח – meat of a calf which swelled to a כביצה (the minimum shiur for tumah), ובשר זקנה שנתמעך – and the meat of an old [cow] which shrank to less than a כביצה, משתערין לכמות שהן – are assessed as they are. Some Amoraim read this Mishnah as "כמות שהן" – [they are measured] as they are now, whereas others read it as "לכמות שהיו" – as they were originally. After several challenges are posed to these opinions, Rabbah clarifies the machlokes: if the meat was initially a כביצה, but shrank and is currently less than a כביצה, all agree it is not subject to tumah. If it initially was not a כביצה, and currently is a כביצה, all agree it is subject to tumah, but only מדרבנן. Their argument is only כגון שהיה בו כשיעור וצמק וחזר ותפח – where it originally had the requisite measure, then shrank to less than a כביצה, and then swelled back to its original volume. They argue whether or not יש דיחוי באיסורא – there is a concept of rejection regarding laws of prohibition, such as tumah, (i.e., once it is disqualified from tumah, it remains disqualified). However, a Mishnah proves that there is no דיחוי for איסור.

A Baraisa states: תורמין תאנים על הגרוגרות במנין – we separate [maaser] from fresh figs for dried figs by number, not volume. This apparently proves that shrunken items are measured according to their original volume, because if they are measured according to their current volume, then separating by number for dried figs (which have shrunken is מרבה במעשרות – separating excessive maaser (since the fresh figs are more than ten percent of the dried figs’ volume). A Baraisa teaches that if one separates excessive maaser, פירותיו מתוקנים ומעשרותיו מקולקלין – his produce is rectified for consumption, but his maaser is ruined (since maaser must be exactly ten percent, any excess amount remains tevel and prohibits the mixture)!? The Gemara counters that the סיפא of this Baraisa indicates the opposite, because it teaches that one separates maaser from dried figs for fresh figs במדה – by volume, not by number. This apparently proves we assess according to current volume!? The Gemara ultimately explains that both cases are discussing terumas maaser, and following Abba Elazar ben Gomel’s opinion that תרומת מעשר is compared to terumah, and is given בעין יפה – in a generous way (not strictly ten percent).