And he added yet to speak before Him, and said, Perhaps there may be forty found there; ten for each city of the four cities, and Zoar, whose guilt is lighter, forgive thou for Thy mercy's sake. And he said, I will not make an end for the sake of the forty innocent ones.
Forty Righteous and a Plea for Zoar's Lighter Guilt
Targum Pseudo-Jonathan on Genesis 18:29