Parashas Metzora · Passuk 14:17
Chabad.org — English translation + Rashi
Torah Temima points to Toras Kohanim.
English: “Upon the blood of the asham” — that the blood should precede the oil. Or perhaps it means only if blood is still present may he place [the oil], but if there is no blood he may not place it? Therefore the verse says “to the place of the blood of the asham” — it is not the blood that causes [the validity] but the place that causes it.
Order and location
Chazal teach that the oil is placed on the same spot where the blood was placed; the presence of residual blood is not required, only the correct location.