Mishneh Torah — Transmission of the Oral Law מסירת תורה שבעל פה, Chapter 39

וְעוֹד חִבְּרוּ הֲלָכוֹת פְּסוּקוֹת, בְּעִנְיַן הָאָסוּר וְהַמֻּתָּר וְהַחַיָּב וְהַפָּטוּר, בִּדְבָרִים שֶׁהַשָּׁעָה צְרִיכָה לָהֶם, כְּדֵי שֶׁיִּהְיוּ קְרוֹבִין לְמַדַּע מִי שְׁאֵינוּ יָכוֹל לֵירַד לְעָמְקוֹ שֶׁלַּתַּלְמוּד. וְזוֹ הִיא מְלֶאכֶת ה' שֶׁעָשׂוּ בָּהּ כָּל גְּאוֹנֵי יִשְׂרָאֵל, מִיּוֹם שֶׁחֻבַּר הַתַּלְמוּד וְעַד זְמָן זֶה, שְׁהוּא שָׁנָה שְׁמִינִית אַחַר מֵאָה וְאֶלֶף לְחָרְבָּן.

Also, [the Geonim] composed [texts recording] the decisions of Torah law regarding what is permitted and what is forbidden, when one is liable and when one is free of liability, with regard to subjects that were necessary at the time, so that they would be accessible to the grasp of a person who could not comprehend the depths of the Talmud. the She'iltot of Rav Achai Gaon, and the Halachot of Rav Yitzchak Alfasi. This is the work of God, which was performed by all the Geonim of Israel from the completion of the Talmud until the present date, 1108 years after the destruction of the Temple, 4937 years after the creation of the world. over a number of years, constantly revising his work. Thus, in Hilchot Kiddush HaChodesh 11:16, he mentions the date of the composition of the text as 4938, one year later, and in Hilchot Shemitot V'Yovalot, he mentions the date 4936, one year earlier.