RASHI’S SOURCE
The proof for Rashi’s interpretation of pshat is alluded to by another amendment that Rashi makes to the Gemara’s wording in his commentary: In the Gemara, this exposition, “this implies that she is impure,” is made on the clause “and she will thus be rid of this impurity” at the end of the section — “the kohen must first effect atonement for her and she will thus be rid of this impurity.” Rashi, however, cites this exposition in his commentary on the preceding verse: “He shall offer it before Hashem and atone for her, and she shall become purified from the source of her blood.”
Seemingly, since Rashi teaches, “This implies that up to this point (she) is called impure” — meaning that she is already not impure, and only has the name denoting impurity — it would seem more fitting for him to bring this exposition in his commentary on the word, “הָרֵהָטְו {and she will thus be rid of this impurity}” (where the hei has the tzeirei vowel) that appears at the end of this section, rather than on the word “הָרֲהָטְו {and she shall become purified} (where the hei is vowelized with a patach) from the source of her blood,” — which emphasizes her active purification from impurity!
The explanation: If not for the verse, “and she shall become purified from the source of her blood” we would have thought that the prohibition to eat sacrificial foods is totally unrelated to impurity, but instead comes from a separate prohibition — because she still lacks the benefit that comes with bringing a sacrifice;
However, the verse’s wording — “and she shall become purified from the source of her blood” — adds a critical nuance: It suggests that her purity remains incomplete not merely because she has failed to bring a sacrifice, but also because impurity remains “from the source of her blood.”
How does this verse square with the verse saying that the thirty-three days are already called “her days of purity”? We must say, "This implies that up to this point (she) is called impure”: Although her impurity was removed, she is still labelled impure.
