משך חכמה — זאת תהיה תורת המצורע ביום טהרתו

Q — Where in our parsha is the principle of R' Acha hinted — that illness depends on the person himself ("ממך... שלא יבואו חוליים עליך")?

A — The Torah uses "המיטהר" (התפעל — reflexive/causative) rather than the passive "הנטהר." Had it said the latter, the metzora would be one acted upon; "המיטהר" indicates that he himself brings about his purification — "שמסיבת תשובתו להשי״ת הוסר מאתו הנגע." Tzaraat lifts only when the person himself effects the change.