Esau did not really shrink back from parricide, only it chanced not to fit the plan he had hatched. "If Ishmael slays my father," he said to himself, "I am the rightful redeemer, and I shall kill Ishmael to avenge my father, and if, then, I murder Jacob, too, everything will belong to me, as the heir of my father and my uncle." This shows that Esau's marriage with Mahalath, the daughter of Ishmael and grandchild of Abraham, was not concluded out of regard for his parents, who were opposed to his two other wives, daughters of the Canaanites. All he desired was to enter into amicable relations with Ishmael in order to execute his devilish plan.
Esau Plotted to Murder Both Jacob and Isaac
Legends of the Jews 6:87