Parashas Metzora · Passuk 15:13
Chabad.org — English translation + Rashi
Torah Temima points to Megillah 8b.
English: “And he shall be pure” — what is “and he shall be pure”? He is now pure from conveying impurity to earthenware by heset; even if he later has a sighting, he does not convey impurity retroactively [to that earthenware].
Limited effect of immersion before nightfall
Chazal give immersion immediate effect regarding earthenware heset, even though full purity still awaits sunset.