Jamieson, Fausset and Brown on Obadiah 1:10

10. against thy brother--This aggravates the sin of Esau, that it was against him who was his brother by birth and by circumcision. The posterity of Esau followed in the steps of their father's hatred to Jacob by violence against Jacob's seed (Ge 27:41).

Jacob--not merely his own brother, but his twin brother; hence the name Jacob, not Israel, is here put emphatically. Compare De 23:7 for the opposite feeling which Jacob's seed was commanded to entertain towards Edom's.

shame ... cover thee--(Psa 35:26; 69:7).

for ever--(Is 34:10; Eze 35:9; Mal 1:4). Idumea, as a nation, should be "cut off for ever," though the land should be again inhabited.