וְכִֽי־יִטְהַ֤ר הַזָּב֙ מִזּוֹב֔וֹ וְסָ֨פַר ל֜וֹ שִׁבְעַ֥ת יָמִ֛ים לְטָהֳרָת֖וֹ וְכִבֶּ֣ס בְּגָדָ֑יו וְרָחַ֧ץ בְּשָׂר֛וֹ בְּמַ֥יִם חַיִּ֖ים וְטָהֵֽר׃
And when he that hath an issue is cleansed of his issue, then he shall number to himself seven days for his cleansing, and wash his clothes; and he shall bathe his flesh in running water, and shall be clean.
Rashi on Leviticus
וכי יטהר means WHEN HE CEASETH [FROM HIS ISSUE] (Sifra, Metzora Parashat Zavim, Chapter 5 1).
Siftei Chakhamim
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.”
Chizkuni
לטהרתו, “after his process of purification has begun when the emission has stopped and seven days had elapsed.