v.1 - Throughout this book Obadiah is going to be prophesying about God's judgment of the people of Edom. The question is - what did the people of Edom do? Well, as we will see Obadiah speak of throughout the chapter...the people of Edom betrayed Israel during occupation by the Babylonian Empire. They helped captured fleeing Israelites and brought them back to the Babylonians and they also took part in the looting of Jerusalem.
v.10-11 - "Your brother Jacob" - what does this mean? The Edomites were descendants of Esau which means they were actually hereditary cousins to the people of Israel. So not only did they betray God's people, but they betrayed their own flesh and blood, and as the pagan Babylonians entered into Israel raping ad pillaging...the Edomites did the same. Though God had ordained the judgment of Israel through Babylon, it enraged Him that the cousins of Israel would delight in their conquest and participate in it. I would guess that it angers God and breaks His heart when He sees fellow Christians - made into family through the sanctifying blood of Jesus Christ - hurting one another, betraying one another, delighting in one anothers' failure. The Body of Christ should be a place of safety and love.
v. 15 - God is absolutely just...He cannot be unjust. When injustice happens in the world it will have to come face to face with the wrath of our all-powerful, just God. The Edomites sins were poured back on them and they were crushed. Through the blood of Jesus Christ we have been freed from the crushing death f our own sins, if we choose to believe. I hope that is where you place your trust.
v. 17-18 - Though judgment has been unleashed on Israel through Babylon, there will be survivors - a remnant. Edom will not be shown the same kind of mercy. For going to war against the people of God and betraying their own blood, they will be like the stubble on the fields after the harvest that is burned away - there will be nothing left. Within 100 years of this prophesy, Edom was in ruins and has ceased to exist. It never ends well when you set yourself against God and His people.