Mishneh Torah — Transmission of the Oral Law מסירת תורה שבעל פה, Chapter 23

רַבִּינָא וְרָב אַשֵׁי, הֶם סוֹף חַכְמֵי הַתַּלְמוּד; וְרָב אַשֵׁי הוּא שֶׁחִבַּר הַתַּלְמוּד הַבַּבְלִי בְּאֶרֶץ שִׁנְעָר, אַחַר שֶׁחִבַּר רִבִּי יוֹחָנָן הַתַּלְמוּד הַיְּרוּשְׁלְמִי בִּכְמוֹ מֵאָה שָׁנָה.

Ravina and Rav Ashi were the final generation of the Sages of the Talmud. Rav Ashi composed the Babylonian Talmud in Shin'ar approximately one hundred years after Rabbi Yochanan composed the Jerusalem Talmud. 86a, which relates that "Rav Ashi and Ravina were the final authorities with regard to instruction," as the source for the Rambam's statements. From the Rambam's later statements, it appears that in this instance as well, Rav Ashi laid the foundation for the Talmud. However, the composition of the text was completed by Ravina Zuta, Mar bar Rav Ashi, and Rav Yosse more than seventy years after Rav Ashi's death.