Do you mean Parshas Chayei Sara by any chance?
Parshas Chayei Sara Malbim – An Important Shidduch Lesson
Avrohom had three good friends who believed in Hashem, Aner Eshkol and especially Mamrei who gave him advice to go through with his Bris Mila. Yet not only did Avrohom reject their daughters as suitable matches for Yitzchok, but he went as far as making Eliezer swear that he will not turn to them for a Shidduch. Instead Avrohom told him to to go to his own family, to the land Nachor his brother, where Idol worship was rampant. Why did Avrohom, the battler against avodah zara, show such a degree of nepotism?
The Malbim brings from the Ran that aveiros in the Torah come in two forms, those that destroy the neshama such as bad hashkafos, and those that affect the guf as well, which include bad middos such as jealousy and anger that make the body stir. In the latter case this nature is passed down through the generations, as children often can suffer from the same character flaws as their parents. This was the case of the Kenanim and therefore Avrohom did not want to be Mishadech with them.
Nachor’s problem was purely religious philosophy. This affected the soul and not the genes. It was a mind problem that would not necessarily affect future generations, who may reach thewir own conclusions. Religion is more easily reparable and parents are not an indication of their children. Bad middos are trickier and not likely to disappear. Something to keep in mind when choosing a Shidduch. Avrohom did!