By thy sword shalt thou live; by violence and rapine, in an unquiet and military posture, troubling others, and forced to defend thyself. But this, as also the following clause, though spoken to Esau, was not fulfilled in him, but in his posterity the Edomites, whose history makes good this prophecy. Thus things spoken and promised to Abraham were fulfilled in his posterity, as Genesis 12:3, Genesis 22:18. When thou shalt have the dominion; when thou shalt grow potent. Some render the words thus, When thou shalt have mourned or groaned, as the same word is used Psalms 55:2; when thou hast oppressed as long as I think fit.
Related Commentaries of Genesis 27:40
Genesis 27:40
40 And by thy sword shalt thou live, and shalt serve thy brother; and it shall come to pass when thou shalt have the dominion, that thou shalt break his yoke from off thy neck.