Or HaChaim on Genesis 18:23/אור החיים על בראשית י״ח:כ״ג

1 ויגש אברהם. Abraham approached, etc. When G'd had mentioned כלה, He meant that all the people in Sodom were doomed by the attribute of Justice; should it be G'd's intention to save the individual good people by allowing them to escape as happened to Lot, Abraham argued that perhaps there would be a substantial number of such people, i.e. fifty. The words האף תספה, "Will You also wipe out, etc?" mean "will You still wipe out the wicked despite the presence of so many innocent people?" The presence of the fifty should protect the entire population against mass destruction. When Abraham referred to the fifty good people as בקרבה, in the midst of the city, he implied that they should not be made to move in order to be saved. G'd would do better to remove the guilty and destroy them elsewhere. He used the expression חלילה לך, "it would be a profanation of Your name," when he referred to the remote possibility that the innocent actually share the fate of the guilty; concerning his second request that the presence of the righteous should serve as an umbrella for the guilty, he realised that this would be an act of kindness, not justice.

2When Abraham said והיה כצדיק כרשע, that the righteous would wind up just like the wicked, he indicated that if G'd applied the same yardstick to all creatures alike, the righteous would be deprived of every incentive to be righteous.

3The second time Abraham used the expression חלילה לך, he referred to the second alternative of saving the wicked because of the presence of a substantial number of righteous people in their midst. Abraham did not want G'd to destroy the wicked under such circumstances. Another meaning of this plea could be that Abraham reminded G'd that He had sworn after the deluge not to bring on mass destruction on mankind by invoking the ultimate rigor of the attribute of Justice (compare our comments on Genesis 9,11).