Horayot 2B

זו ואין צריך לומר זו קתני.

The Talmud answers: In the latter clause, the tanna teaches the Mishnah employing the style: This, and it is unnecessary to say that, i.e., the cases are arranged with each case more obvious than the one that preceded it.

וידע אחד מהן שטעו או תלמיד וראוי להוראה. תרתי למה לי? אמר רבא: איצטריך, סלקא דעתך אמינא הני מילי גמיר וסביר, אבל גמיר ולא סביר ⁠– לא.

§ The Mishnah teaches: And one of the judges knew that they erred, or if he was a student and he is qualified to issue halakhic rulings. The Talmud asks: Why do I need two cases? As a student qualified to issue halakhic rulings is the equivalent of one of the judges, why did the tanna mention both? Rava said: It was necessary to state both, as it may enter your mind to say that this statement that he is liable applies specifically to one who is learned and analytical, but that one who is learned but not analytical, no, he should not be liable to bring an offering. Therefore, the tanna cites both the case of a judge and the case of a student qualified to issue halakhic rulings, to teach that even one who is learned but not analytical is liable in this case.

אמר ליה אביי: להוראה גמיר וסביר משמע! אמר ליה, אנא הכי קאמינא: אי מההיא ⁠– הוה אמינא הני מילי גמיר וסביר, אבל גמיר ולא סביר ⁠– לא, תנא ראוי להוראה, ממשנה יתירה: אפילו גמיר ולא סביר, סביר ולא גמיר.

Abaye challenged this and said to Rava that the term: A student qualified to issue halakhic rulings, indicates that he is both learned and analytical. Rava said to Abaye: This is what I am saying: If the tanna had taught the halakha from that first halakha with regard to one of the judges, I would say that this statement applies only to one who is both learned and analytical, but if he was learned and not analytical, no, he would not be liable. Therefore, the tanna taught the additional case of a student qualified to issue halakhic rulings, and from the extraneous case in the Mishnah one can infer that the halakha applies even to one who is learned but not analytical or one who is analytical but not yet learned. Since he associates his action with himself, he is liable.