The Torah teaches that a kohen cannot marry a halala – a woman who is the product of a forbidden sexual relationship or one who has engaged in a forbidden sexual relationship. The question with which our Gemara grapples is whether the daughter of a kohen has a similar prohibition from marrying a halal. We find that two young scholars – Rav Pappa and Rav Huna, the son of Rav Yehoshua – were visiting their teacher, Rav Idi bar Avin, when they were discussing this issue. Rav Pappa suggested that the answer can be learned from our Mishna, where it lists which groups of people can marry one another. Since the Mishna does not specifically permit this case, we can conclude that it is forbidden. Rav Huna disagreed, arguing that the Mishna proves nothing, since it is only teaching about groups of people whose relationships will be the same no matter whether the man and woman are from one group or the other. Given the fact that a kohen cannot marry a halala, even if the daughter of a kohen is allowed to marry a halal, it would not appear on this list.
Upon presenting their discussion to Rav Idi bar Avin, he looked at them and said “dardekai (youngsters), are you not familiar with the teaching of Rav Yehuda in the name of Rav that the daughter of a kohen is permitted to marry a halal?!”
Rav Idi bar Avin was a Babylonian amora of the third and fourth generation. The story is told about his father, Rav Avin Naggara, that he was extremely meticulous about the mitzva of lighting candles for Shabbat, and Rav Huna told him that because of his diligence he would merit children who would become Sages. In fact we know of two of his children – Rav Hiyya and Rav Idi – both of whom fulfilled that prophecy.
Rav Idi was a student of Rav Hisda, although we find that he quotes other Sages’ teachings, as well. We find him actively involved in discussions with his peers, and in particular with Abaye. He lived an extraordinarily long life, which is why we find him referring to his students Rav Pappa and Rav Huna as dardekai – youngsters.