Commentators unanimously emphasize that Edom's sin was severely aggravated because it was "violence against thy brother Jacob." Calvin calls it "barbarous inhumanity." The use of the name "Jacob" was intentional, reminding Edom of their shared ancestry from twin brothers. This betrayal violated not only natural family bonds but also God's specific command for Israel to not abhor an Edomite (Deut. 23:7), making the sin particularly heinous.