1. Source of the machlokes about guarding terumah which is ספק טמא from certain tumah

The Gemara explains the source of the machlokes whether terumah which became ספק טמא must be protected from definite tumah: the passuk says ואני הנה נתתי לך את משמרת תרומתי – and behold, I have given you the safeguard of my terumos. The Gemara first explains that Rebbe Eliezer holds the plural implies that בשתי תרומות הכתוב מדבר – the passuk is discussing two cases of terumah: tahor terumah and תרומה תלויה – “suspended” terumah (i.e., possibly tamei), and about both it said עביד לה שימור – make a safeguard for it. Rebbe Yehoshua holds "תרומָתִי" כתיב – it is written “my terumah” (singular). However, this explanation is rejected, because Rebbe Eliezer also primarily follows the written form. The Gemara therefore explains that Rebbe Yehoshua holds the word "לך" – for you implies: הראויה לך שמור – [terumah] which is fit for you, guard, ושאינה ראויה לך לא תשמור – but that which is not fit for you, you need not guard. Rebbe Eliezer holds that terumah which is ספק טמא is also "ראויה", because שמא יבוא אליהו ויטהרנה – Eliyahu might come and declare it tahor.

1. Penalizing one who was צורם אוזן בבכור

The next Mishnah states: הצורם אוזן בבכור – if [a Kohen] nicks a bechor’s ear, making it blemished, Rebbe Eliezer says הרי זה לא ישחוט עולמית – he may never shecht it, even if it develops another מום. The Chochomim say: נולד בו מום אחר ישחוט עליו – when another blemish develops in it, he may shecht on its basis, since he does not gain from the מום he inflicted. The Gemara asks that both opinions contradict themselves: although one whose נגע of צרעת was cut off unintentionally becomes tahor, קצצה מתכוין – if he cut it off intentionally, Rebbe Eliezer says if he develops another נגע, he can become tahor based on it (because we assume that if the second נגע becomes tahor, the first would have also healed). The Chochomim say he remains tamei unless the נגע spreads over his whole body (which would make him tahor even if the first נגע was still there), or if he had cut it out when it was smaller than a גריס. Thus, Rebbe Eliezer here does not penalize him forever, and the Chochomim do, the reverse of their positions in our Mishnah!? The Gemara proceeds to distinguish between the two cases.

1. צורם אוזן בבכור ומת מהו לקנוס בנו אחריו

Rebbe Yirmiyah asked Rebbe Zeira: צורם אוזן בבכור ומת – if one nicks a bechor’s ear and then dies, מהו לקנוס בנו אחריו – what is the halachah regarding penalizing his son after him to prohibit him from shechting the bechor? This cannot be resolved from similar cases: even if, where one sold a slave to an idolator and died, his son is likewise penalized to redeem him, that may be because כל יומא ויומא מפקע ליה ממצות – every day he remains with the idolator, he prevents him from performing mitzvos. On the other hand, even if, where one scheduled work for Chol Hamoed and died, his son is not penalized (and may perform the work), that may be because the father never actually worked on Chol Hamoed. Here, what is the halachah if one nicks a bechor’s ear and dies? לדידיה קנסו רבנן – Did the Rabbis penalize him specifically, והא ליתיה – and he is no longer here, or לממוניה קנסו רבנן – did the Rabbis penalize his property (the bechor), and that still exists? This is resolved from a ruling about shemittah, that if someone fertilized his field, he may not plant it in the eighth year, yet if he dies, his son may plant it. Here, too, the son may shecht the bechor.