God is a righteous God, but his righteousness demands wrath against sin. In the book of Nahum, God announces that he is against a nation – the nation of Assyria. While this is extremely bad news for the Ninevites, for God’s people, this is really good news. The message is one of wrath against their enemies. Israel would rejoice at this message, and also at their return from Babylon in 536 BC, but they will rejoice even more when their Messiah returns! This verse, and the one that Nahum likely quoted from Isaiah, are used by Paul to speak of the good news of the Gospel going out to the ends of the world.
God tells the people of Nineveh to prepare for the advancing army, yet this too is ironic because no amount of preparation will help them. When God sets himself against a nation, there is nothing that can stop him!
Fortunately, for believers God is on our side. “What, then, shall we say in response to these things? If God is for us,who can be against us?” Romans 8:31. Jesus bore God’s wrath against our sin. Now God is on our side! We never have to fear God being against us!