For I have known him, in order that he may command his children and his household after him to keep the way of Hashem by doing righteousness and justice, so that Hashem may bring upon Avraham that which He has spoken concerning him.
English: “For I have known him.” Rabbi Elazar said: From the blessing of the righteous you learn the curse of the wicked. As it is written, “For I have known him… to do righteousness and justice,” and immediately afterward it is written, “And Hashem said, ‘The outcry of Sedom and Amorah is great.’”
On the daf / in context: The juxtaposition teaches that the same divine knowledge that chooses Avraham for righteousness also exposes the opposite quality of Sedom.
Type of Learning
Derash on the verse (Bavli sugya) — not a formal named middah of the 13. Adjacent verses supply a contrast between the righteous and the wicked.
What Is Learned
From the blessing attached to Avraham’s righteousness one learns the corresponding judgment upon the wicked of Sedom.