R Yitzchok brings a proof from Sarai and Avrom re Hagor that one who calls on Hash-m to judge another is judged themself first. Therfore Sora eimeinu died at an earlier age than did Avrahahm avinu.
R Yitzchok himself then brings a proof from Hash-m changing Sarai's name to Sora that shinui hashem can nullify and negative gezerah (being childless).
The obvious question is that since the maase with Hagor took place when her name was still Sarai shouldn't it have been nullified when Hash-m changed her name to Sora?
Gary Schreiber, Chicago
There is no rule which guarantees that a name-change negates all harsh decrees. What Chazal mean is that changing one's name increases one's chances of this happening. (You yourself inserted the word 'can'.)
In the case of Sarah, Hash-m wanted to negate the decree of childlessness, with regards to both Avraham and Sarah, so He changed their names, to enable this powerful miracle to happen.
To be sure, changing Sarah's name might have negated Sarah's punishment, but it didn't:
1. maybe because it was not changed specifically for this purpose,
2. maybe because Sarah brought the punishment on herself, whereas childlessness was caused by Hash-m,
3. maybe because it requires Tefilah as well, and Sarah did not pray for it,
maybe for some other reason. In any event, the fact that Shinuy Hash-m helped with regard to one thing and not with regard to another is feasible and is not a Kashya on the principle.
be'Virchas Kol Tuv