Thus saith the LORD; For three transgressions of Edom, and for four, I will not turn away the punishment thereof; because he did pursue his brother with the sword, and did cast off all pity, and his anger did tear perpetually, and he kept his wrath for ever:
For three transgressions of Edom ... because he did pursue his brother with the sword - (Isaiah 34:5). The chief aggravation to Edom's violence against Israel was, that they were twin brothers, and had the same parents, Isaac and Rebecca (cf. Genesis 25:24-26). The Mosaic law had enjoined the Israelite, therefore, to be kind to the Edomite, "Thou shalt not abhor an Edomite; for he is thy brother ... The children that are begotten of them shall enter into the congregation of the Lord in their third generation" (Deuteronomy 23:7-8). On the other hand, Edom is punished for his unbrotherly conduct to Israel, "For thy violence against thy brother Jacob shame shall cover thee, and thou shalt be cut off forever ... thou shouldest not have looked on the day of thy brother in the day that he became a stranger; neither shouldest thou have rejoiced over the children of Judah in the day of their destruction" (Obadiah 1:10; Obadiah 1:12; Malachi 1:2).
And did cast off all pity - literally, destroy compassions - i:e., did suppress all the natural feeling of pity for a brother in distress.
And he kept his wrath forever - as Esau kept up his grudge against Jacob, because having twice supplanted him-namely, as to the birthright and the blessing (Genesis 27:41), so Esau's posterity against Israel (Numbers 20:14; Numbers 20:21). Israel's wars with Edom had been defensive, not aggressive. The valley of salt (2 Samuel 8:13), when David had defeated them, was within the borders of Judah (Joshua 15:62). Psalms 60:1-12 speaks of severe suffering inflicted by Edom. To restrain their violence, Edom had been garrisoned by David. In Jehoshaphat's days, again, when he was weakened by defeat at Ramoth-gilead, Edom joined Moab and Ammon in the effort to cast out Judah from his inheritance (2 Chronicles 20:10-11): and yet Judah, though restraining Edom by garrisons, had not taken away any of Edom's land. Edom first showed his spite in not letting Israel pass through his borders when coming from the wilderness, but threatening to "come out against him with the sword;" again, when the Syrians attacked Jerusalem under Ahaz, "The Edomites came and smote Judah, and carried away captives" (cf. 2 Chronicles 28:17 with 2 Kings 16:5); next, when Nebuchadnezzar assailed Jerusalem (Psalms 137:7). In each case Edom chose the day of Israel's calamity for venting his grudge. This is the point of Edom's guilt dwelt on in Obadiah 1:10-13. God punishes the children, not for the sin of their fathers, but for their own filling up the measure of their father's guilt, as children generally follow in the steps of, and even exceed, their father's guilt (cf. Exodus 20:5).