Positive commandment · Mitzvat Aseh #30 of 613
To remove the ashes from the altar
לְהָרִים הַדֶּשֶׁן מֵעַל הַמִּזְבֵּחַ בְּכָל יוֹם
The verse · Vayikra 6:3
וְלָבַשׁ הַכֹּהֵן מִדּוֹ בַד וּמִכְנְסֵי־בַד יִלְבַּשׁ עַל־בְּשָׂרוֹ וְהֵרִים אֶת־הַדֶּשֶׁן אֲשֶׁר תֹּאכַל הָאֵשׁ אֶת־הָעֹלָה עַל־הַמִּזְבֵּחַ וְשָׂמוֹ אֵצֶל הַמִּזְבֵּחַ
“And the priest shall put on his linen garment, and his linen breeches shall he put on his flesh, and take up the ashes which the fire has consumed with the burnt offering on the altar, and he shall put them beside the altar.”
The Rambam’s words
To remove the ashes from the altar, as [Leviticus 6:3] states: "And he shall remove the ashes...."
לְהָרִים הַדֶּשֶׁן מֵעַל הַמִּזְבֵּחַ בְּכָל יוֹם, שֶׁנֶּאֱמָר: "וְהֵרִים אֶת הַדֶּשֶׁן" (ויקרא ו, ג).
Why · Sefer HaChinuch #131
Lifting of the ashes
“From the roots of the commandment are what you will see at the end of my words. However, I am afraid of drawing close to the Dwelling of G-d, as I know that “anyone who comes close, who comes close” that has not sufficiently sanctified himself “will not see the House and live.””
Who & when
“And it is practiced at the time of the [Temple] by the males of the priesthood.”
Where in the Mishneh Torah
Hilchot Daily Offerings and Additional Offerings הלכות תמידים ומוספין