John Gill Commentary Genesis 18:31

"And he said, Behold now, I have taken upon me to speak unto the Lord: peradventure there shall be twenty found there. And he said, I will not destroy it for the twenty`s sake." — Genesis 18:31 (ASV)

And he said, behold now, I have taken upon me to speak unto
the Lord (See Gill on Genesis 18:27):

Peradventure there shall be twenty found there ;
wouldest thou destroy it, such a number being in it; or, wouldest thou spare it for their sakes?

and he said, I will not destroy [it] for twenty's sake ;
if there were no more in it, I would spare it for their sake.