In his introduction to Eight Chapters Rambam writes:
וְדַע, שֶׁהַדְּבָרִים אֲשֶׁר אֹמַר בִּפְרָקִים אֵלּוּ וּבְמַה שֶּׁיָּבֹא מִן הַפֵּרוּשׁ, אֵינָם דְּבָרִים שֶׁבְּדִיתִים מֵעַצְמִי, וְלֹא פֵרוּשִׁים שֶׁחִדַּשְׁתִּים. אָמְנָם הֵם עִנְיָנִים לִקַּטְתִּים מִדִּבְרֵי חֲכָמִים בְּמִדְרָשׁוֹת וְתַלְמוּד וְזוּלָתָם מֵחִבּוּרֵיהֶם; וּמִדִּבְרֵי הַפִּילוֹסוֹפִים גַּם כֵּן הַקַּדְמוֹנִים וְהַחֲדָשִׁים, וּמֵחִבּוּרֵי הַרְבֵּה בְנֵי אָדָם - וּשְׁמַע הָאֱמֶת מִמִּי שֶׁאֲמָרָהּ.
Know, however, that the ideas presented in these chapters and in the following commentary are not my own invention; neither did I think out the explanations contained therein, but I have gleaned them from the words of the wise occurring in the Midrashim, in the Talmud, and in other of their works, as well as from the words of the philosophers, ancient and recent, and also from the works of various authors, as one should accept the truth from whatever source it proceeds.
(Gorfinkle translation)