Rabbi Yehuda haNasi and Rabbi Natan were the last from the Mishna period and Ravina and Rav Ashi were the last of the Talmudic period. This statement is likely referring to the editing of the Mishna and Talmud. Raba bar Nachmani was killed out of fear of the king. Raba bar Nachmani's tragic death is recounted and how it related to the need for him in the heavens to resolve a debate between God and the rabbis in the yeshiva in the heavens. The Mishna related to the custom in the land and a story about Rabbi Yochanan ben Matia and his son's commitment to their workers. On account of that story, the Gemara digresses into a series of drashot on the story of Avraham and the angels and the food that he served to them.