Eruvin 30 - 36
“Sinai said two (eggs).”
This statement is found on our daf to teach the amount of food needed to fulfill the mitzvah of eruvei chatztzerot — the rabbinical mitzvah that permit people to carry items from their homes into their common courtyard and from the yard into their homes —if (raw) eggs are used for the eruv.
Who was this mysterious “Sinai” who taught aforementioned amount? Rashi explains that he was Rav Yosef, and was referred to as “Sinai” (as we find Rav Yosef called by this name at the end of Mesechta Berachot and the end of Mesechta Horiyot), since he was an exceptional Torah expert in the knowledge of the mishnayot and beraitot.
- Eruvin 30a
“Rav Chanina Choza’a said, ‘It can be assumed with certainty (Heb. - chazaka) that a Torah scholar will not allow any unfinished item out go out of his hand.”
This statement was made regarding finding fruits left by a Torah scholar and one is unsure whether the required terumot and ma’asorot separations were made. The sage teaches that it is a halachic presumption that everything required was already done. Rashi states that since the fruit is his and it is his obligation to make the required separations, he is careful not to “fix” the fruit so that he would not be potentially be “placing a stumbling block before the blind”, as it were, in the event that another person should eat it in its forbidden state.
- Eruvin 32a
