רב אחא

Rav Acha and Ravina are colleagues. The Tosafot wrote in the chapter "The One Who Asks About the Cow" [(l'm)] that they are earlier than Rav Pappa, and it does not appear that in the first chapter of Chulin Ravina and Rav Acha, the son of Rava, were sitting before Rav Ashi, and likewise in the chapter "The One Who Asks" Rav Acha and Ravina were before Rav Ashi and Amemar. And we have already written above that this is Rav Acha, the son of Rava. [(See above regarding Rav Acha, the son of Rav, for there are ancient Rav Acha and Ravina.) In all of Torah, Ravina is lenient, and Rav Acha is stringent, and a sign for you is "8, 8" (Hilkhot Olam).

And the halacha is according to Ravina alone, except for three cases where Rav Acha is lenient, and the halacha is according to Rav Acha (Chulin (83b), Pesachim (74b), and there is a question in Avodah Zarah (33b) and Yevamot (39b). Hilkhot Olam wrote in section 35b that this is when there are no others disputing with them. The response of Chavat Yair wrote, "I did not understand and I did not find." In the Jerusalem Talmud, Ma'aser Sheni, chapter 5, halacha 5, it is stated that he did not take Ma'aser, indicating that he was a Kohen (see there) regarding Rav Acha, the son of Ravina, explicitly stated that he was a Kohen.]