Parsha Vayeira - Beresheit - Chapter 18 - Verses 20-23
From these verses we learn the tremendous lesson that we should never judge anyone. We should go down to their level no matter how they seem in our eyes. Despite the fact that Hashem saw the people of Sodom and their outrageous behavior, he said, I am going to "go down" - I am going to go deeper to see if there is some merit.
From Verse 22 we learn that the preparation to pray is to know who you are standing before. We are praying directly before Hashem and we are standing right before him.
In the next verses we will learn the great efforts Avraham put in tefilah for the people of Sodom before Hashem decides to destroy them. No matter how wicked he thought they were, he did not let any of his personal feelings get involved. He loved people and he believed in the goodness of every person.