Avodah Zarah 32B

אין עליו קורט דם ⁠— מותר. אמר רב הונא: לא שנו אלא שלא מלחו, אבל מלחו ⁠— אסור. אימא: מלחו העברתו.

If it does not have a trace of blood upon it, then it is permitted. Rav Huna says: They taught that a bloodless hide is permitted only in a case where the non-Jew did not salt it, but if he salted it, it is prohibited, as I say: Its salting removed the trace of blood.

רבן שמעון בן גמליאל אומר: בזמן שהקרע שלו עגול ⁠— אסור, משוך ⁠— מותר. אמר רב יוסף, אמר רב יהודה אמר שמואל: הלכה כרבן שמעון בן גמליאל.

§ The Mishnah teaches that Rabban Shimon ben Gamliel says: A hide is prohibited only when the tear around its heart is circular, but if it is elongated, it is permitted. The Talmud notes: Rav Yosef says that Rav Yehuda says that Shmuel says: The halakha is in accordance with the opinion of Rabban Shimon ben Gamliel.

אמר ליה אביי: הלכה ⁠— מכלל דפליגי? אמר ליה: מאי נפקא לך מינה? אמר ליה: גמרא גמור, זמורתא תהא?

Abaye said to Rav Yosef: If one rules that the halakha is in accordance with the opinion of Rabban Shimon ben Gamliel, does that mean by inference that the Rabbis disagree, or perhaps there is no dispute and everyone accepts the opinion of Rabban Shimon ben Gamliel? Rav Yosef said to him: What difference is there to you whether or not the Rabbis disagree? In either case the halakha is in accordance with the opinion of Rabban Shimon ben Gamliel. Abaye said to him, invoking a folk expression with regard to one who learns without achieving understanding: Is it simply learn the lesson; let it be like a song? In other words, is it sufficient to simply parrot the halakhic ruling? No; it is necessary to examine an issue to understand it even if it does not yield a practical halakhic difference.