Leviticus 6:4

‎ ופשט את בגדיו ‎ AND HE SHALL PUT OFF HIS GARMENTS — This is not compulsory (cf., however, Nachmanides) but it is a matter of decency so that he should not, through removing the ashes, soil the garments in which he has regularly to minister at the altar; in the clothes he wore when he boiled the pot for his master (a menial task) he should not pour out a glass of wine for him (an honourable office). On this account it states: And he shall put on other garments — inferior to those in which he ministers at the altar (Yoma 23b; Shabbat 114a). והוציא את הדשן AND HE SHALL BRING OUT THE ASHES that were heaped upon the ash-heap (not the ashes mentioned in v. 3). When it accumulated and there was no more room on the wood-pile (מערכה) he carried it out; this was not compulsory every day, whilst the תרומת הדשן (the taking out of the pan of ashes commanded in v. 3) was a daily duty (Yoma 20a).

וּפָשַׁט֙ אֶת־בְּגָדָ֔יו וְלָבַ֖שׁ בְּגָדִ֣ים אֲחֵרִ֑ים וְהוֹצִ֤יא אֶת־הַדֶּ֙שֶׁן֙ אֶל־מִח֣וּץ לַֽמַּחֲנֶ֔ה אֶל־מָק֖וֹם טָהֽוֹר׃

And he shall put off his garments, and put on other garments, and carry the ashes outside the camp to a clean place.