The men of the city, of Sodom, surrounded [Lot's] house, young and old, all the people from every quarter.
Bereishit 19:4
Despite the wickedness of the inhabitants of Sodom, Abraham tried to defend them before G-d. In fact, Abraham was the first person in history to speak up in defense of others.
G-d was very pleased when Abraham spoke up in defense of humanity, for in doing so, he was imitating, G-d's own ways. As King David expressed it, "G-d is good to all, and His mercy extends to all his creatures." For this reason, the Midrash teaches us that the world is sustained -- and was even created -- in the merit of Abraham.
Similarly, by defending other people's behavior, finding mitigating factors and reasons for their misdeeds as Abraham did, we become partners in sustaining the world. Moreover, we thereby sustain our own personal "worlds" -- the circles of family, friends, students, and co-workers among whom we live -- arousing G-d's mercy on them and on us.
--From Kehot's
Daily Wisdom #2