Jamieson, Fausset and Brown on Obadiah 1:9

9. cut off by slaughter--Maurer translates, "on account of the slaughter," namely, that inflicted on Judea by Edom (compare Ob 14). The Septuagint, Syriac, and Vulgate connect these words with Ob 10, "for the slaughter, for the violence (of which thou art guilty) against thy brother Jacob." English Version, "cut off by slaughter" (that is, an utter cutting off), answers well to "cut off for ever" (Ob 10). However, the arrangement of the Septuagint gives a better parallelism in Ob 10. "For the slaughter" (1) being balanced in just retribution by "thou shalt be cut off for ever" (4); as "For thy violence (not so bad as slaughter) against thy brother Jacob" (2) is balanced by "shame (not so bad as being cut off) shall cover thee" (3). Shame and extinction shall repay violence and slaughter (Mt 26:52; Re 13:10). Compare as to Edom's violence, Psa 137:7; Eze 25:12; Am 1:11.