Rashi on Leviticus 16:19/רש"י על ויקרא ט״ז:י״ט

1והזה עליו מן הדם AND HE SHALL SPRINKLE UPON IT WITH THE BLOOD — After he has made with his finger the application of the blood upon the horns of the altar he shall make seven sprinklings on its top (עליו signifies "upon it") (cf. Sifra, Acharei Mot, Chapter 4 12).

2וטהרו AND THUS HE CLEANSES IT from the defilement that happened to it in the past,

3וקדשו AND HALLOWS IT for use in the future (Sifra, Acharei Mot, Chapter 4 13)