Or HaChaim on Deuteronomy 8:5/אור החיים על דברים ח׳:ה׳

1 וידעת עם לבבך, "You shall know in your heart, etc." This verse reminds a person to reflect that generally speaking no one makes a point of admonishing and disciplining anyone except his own son, as he is not nearly as interested in the education of others as he is in educating his own son. When a person observes his friend's son commit a wrong he is not as much concerned about this as when the wrong is committed by his own son. When we observe G'd disciplining a Jew this is proof that G'd relates to such a Jew as a father relates to a son. When G'd observes the Gentile nations commit all kinds of abominations, He does not react in the same way as He reacts to sins committed by the Jewish people because He does not relate to the Gentiles in the same way, i.e. as a father. He has not associated His name in an exclusive manner with the Gentiles as He has done with us. This is why He demonstrates His concern every time we depart from the norms of behaviour laid down for us.