Despite Chazal's general hostility toward Esav, they benefitted him with one great deed: his respect for his father Yitzchak. What is the significance of this mitzvah? Apparently Esav refrained from killing Yaakov only out of respect toward his father. Yaakov's sons did not have the same respect for their father, which nearly cost Yosef his life. And what is the difference between Esav and King David?