The grammarians write that there is an instance of the word או (or) where it means אם (if). And this opinion is not in agreement with the opinion of the sages of blessed memory, in which every word has a special meaning on its own. And they interpret it to mean “or if”.

And moreover, when it is written או כי ישוב הבשר החי (But if the raw flesh again be turned into white)⁷⁶⁶, Rabbi Avraham ibn Ezra and the commentators are challenged – the sages of blessed memory explain that it comes to inform that it is not an absolute condition but only a possibility and that they mean to say anytime it is turned into white; this is the meaning of the word או, that it comes to inform of a division or a possibility.

Leviticus 13:12-17 says,ואם פרוח תפרח הצרעת בעור וכסתה הצרעת את כל עור הנגע מראשו ועד רגליו לכל מראה עיני הכהן. וראה הכהן והנה כסתה הצרעת את כל בשרו וטהר את הנגע כלו הפך לבן טהור הוא. וביום הראות בו בשר חי יטמא. וראה הכהן את הבשר החי וטמאו הבשר החי טמא הוא צרעת הוא. או כי ישוב הבשר החי ונהפך ללבן ובא אל הכהן. וראהו הכהן והנה נהפך הנגע ללבן וטהר הכהן את הנגע טהור הוא.(And if the leprosy break out abroad in the skin, and the leprosy cover all the skin of him that has the plague from his head even to his feet, as far as appears to the priest; then the priest shall look; and, behold, if the leprosy have covered all his flesh, he shall pronounce him clean that has the plague; it is all turned white: he is clean. But whensoever raw flesh appears in him, he shall be unclean. And the priest shall look on the raw flesh, and pronounce him unclean; the raw flesh is unclean: it is leprosy. But if the raw flesh again be turned into white, then he shall come to the priest; and the priest shall look on him; and, behold, if the plague be turned into white, then the priest shall pronounce him clean that has the plague: he is clean), using the wordואםfor “And if” at the beginning and the wordאו כיfor “But if”.

According to the Malbim, if instead of sayingאו כי*, the Torah had saidואם, then it would be an absolute condition and it would only be known from this that if it turns into white afterwards then he will be clean, but one might also conclude that then he will be clean forever and if afterwards it is revealed to be raw flesh, he will not become unclean since it had already turned to white. The language*או teaches otherwise⁷⁶⁷.

footnotes: ⁷⁶⁶ Leviticus 13:16. ⁷⁶⁷ Malbim, HaTorah v’HaMitzvah Tazria 93.