פירוש על ויקרא 15:13

וכי יטהר means WHEN HE CEASETH [FROM HIS ISSUE] (Sifra, Metzora Parashat Zavim, Chapter 5 1).

When he stops. That is, the purity [cessation] of blood [i.e. discharge] and not the purity [cessation] of his impurity, for it is written afterwards: “and bathe in running water and he will be purified.”

לטהרתו, “after his process of purification has begun when the emission has stopped and seven days had elapsed.