Rashi on Numbers 4:13/רש"י על במדבר ד׳:י״ג

1ודשנו את המזבח AND THEY SHALL TAKE AWAY THE ASHES FROM THE ALTAR — from the brazen altar.

2ודשנו means, they shall remove the ashes from off it (cf. Rashi on Exodus 27:3).

3ופרשו עליו בגד ארגמן AND THEY SHALL SPREAD A GARMENT OF RED PURPLE THEREON — But the fire that descended from heaven on the altar (cf. Rashi on Leviticus 1:7) lay beneath the garment in the form of a lion during the journeyings; it did not, however, burn it because they inverted a large vessel of copper over it (cf. Yoma 21b).