Esau had already married Canaanite women, and he was aware that this had grieved his parents, Issac and Rebekah. Jacob was told not to marry a Canaanite woman, but instead to marry a woman from his uncle, Laban's tribe. Esau knew he parents were unhappy with his other wives. Why would he make that choice to marry an Ishmaelite woman, when he had to know this would upset his parents?
Genesis 28:1 - 22
ESV - 1 Then Isaac called Jacob and blessed him and directed him, "You must not take a wife from the Canaanite women. 2 Arise, go to Paddan-aram to the house of Bethuel your mother's father, and take as your wife from there one of the daughters of Laban your mother's brother.
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