לכל ונשאתי העיר בתוך צדיקם חמשים בסדם אמצא אם ‘ה ויאמר” (חכו י) “בעבורם המקום
Why does it say “im emtza” in the future tense? Doesn’t Hashem surely know if there are fifty tzaddikim to be found in Sodom?
Harav Aizik Ausband, Rosh Yeshivas Telz Cleveland, explained:
The passuk (19:24) says “V’Hashem himtir al Sodom v’al Amora gofris v’aish,” and Chazal explain (Mechilta Beshalach Parashah 8): “If they did teshuvah, then it is a matar, and if not – gofris v’aish” (and the Targum Yonasan there says the same.)
In light of this we can explain that Hashem said to Avraham as follows: Even if right now there are no tzaddikim in Sodom, still, “if I find in Sodom fifity tzaddikim,” who will repent - even only after the punishment begins, that will be enough for me to forgive the whole city for their sake, and I will send upon them only rain.
Lekach Da’as