As we learned on yesterday’s daf (=page) our Gemara has now turned its attention to questions of terefah – animals that have terminal conditions that will cause them to die – which would render the animal non-kosher.
On today’s daf, Rabbah teaches that if the animal suffered an injury to its esophagus that would ordinarily render it a terefah, even if a membrane grew over that spot it is considered a severe injury and the animal remains a terefah. Furthermore, in the event of an injury, the esophagus cannot be checked by looking at it from the outside; it must be checked on the inside. The Gemara explains that this is relevant specifically in a case where we are unsure whether the animal had been clawed. Inasmuch as the outside of the esophagus is reddish in color, it would difficult to ascertain whether the animal had been injured simply by examining the esophagus from the outside; it is essential to check the inside, which is white.
In this context, the Gemara relates the following story:
There once came, before Rabbah, the case of a bird about which there arose a doubt whether it was clawed or not, and he was about to examine the esophagus from the outside when Abayye said to him, ‘Did you not say: Master, that the gullet cannot be examined from the outside but only from the inside?’ Rabbah at once turned it inside out and examined it and found upon it two drops of blood, so he declared it to be a terefah.
The Gemara explains that this was not an error on Rabbah’s part, rather he was testing Abayye to see his reaction.
The practice of a teacher behaving in a manner that is not correct according to the halakhah appears occasionally in the Gemara, for example regarding Hillel and his student Rabban Yohanan ben Zakkai. The point of this exercise is not only to test the students but also to teach them heightened awareness of what they observe and encourage them to review their studies in a setting of practical application.