Mishneh Torah — Transmission of the Oral Law מסירת תורה שבעל פה, Chapter 41

וּמִפְּנֵי זֶה נָעַרְתִּי חָצְנִי, אֲנִי מֹשֶׁה בֵּירִבִּי מַיְמוֹן הַסְּפָרַדִּי, וְנִשְׁעַנְתִּי עַל הַצּוּר בָּרוּךְ הוּא, וּבִינוֹתִי בְּכָל אֵלּוּ הַסְּפָרִים; וְרָאִיתִי לְחַבַּר דְּבָרִים הַמִּתְבָּרְרִים מִכָּל אֵלּוּ הַחִבּוּרִין, בְּעִנְיַן הָאָסוּר וְהַמֻּתָּר וְהַטָּמֵא וְהַטָּהוֹר עִם שְׁאָר דִּינֵי תּוֹרָה: כֻּלָּן בְּלָשׁוֹן בְּרוּרָה וְדֶרֶךְ קְצָרָה, עַד שֶׁתְּהֶא תּוֹרָה שֶׁבְּעַל פֶּה כֻּלָּהּ סְדוּרָה בְּפִי הַכֹּל – בְּלֹא קֻשְׁיָה וְלֹא פֵּרוּק, וְלֹא זֶה אוֹמֵר בְּכֹה וְזֶה אוֹמֵר בְּכֹה, אֵלָא דְּבָרִים בְּרוּרִים קְרוֹבִים נְכוֹנִים, עַל פִּי הַמִּשְׁפָּט אֲשֶׁר יִתְבָּאַר מִכָּל אֵלּוּ הַחִבּוּרִין וְהַפֵּרוּשִׁין הַנִּמְצָאִים מִיְּמוֹת רַבֵּנוּ הַקָּדוֹשׁ וְעַד עַכְשָׁו.

Therefore, I girded my loins - I, Moses, the son of Maimon, of Spain. it is possible that he had a specific intention in doing so here. Despite his desire and intention for the Mishneh Torah to be universally accepted, he knew that other customs were followed in the Ashkenazic community. By mentioning his country of origin, he could be alluding to the fact that some of the customs he mentioned were specific to Jews of that background (Yayin Malchut). I relied upon the Rock, blessed be He. I contemplated all these texts and sought to compose [a work which would include the conclusions] derived from all these texts regarding the forbidden and the permitted, the impure and the pure, and the remainder of the Torah's laws, all in clear and concise terms, so that the entire Oral Law could be organized in each person's mouth without questions or objections. Instead of [arguments], this one claiming such and another such, [this text will allow for] clear and correct statements based on the judgments that result from all the texts and explanations mentioned above, from the days of Rabbenu Hakadosh until the present.