Where It All Goes Down
You know those stories set in medieval times with dragons and jousting, where there's a damsel in distress locked up in a tower, set to marry someone she doesn't love, but then she somehow gets a note out to a knight in shining armor, who comes and rescues/sleeps with/marries her? Well, if you call the guy she doesn't love the "enemy," the knight in shining armor "God," and the damsel "the speaker of this poem," you'd have a good feel for the setting of this poem.
It begins with the loud, fearsome "knocking" of the battering ram against the big wooden door of a besieged city. If you've seen the battle scene at Helm's Deep for Lord of the Rings: The Two Towers, you know what this looks like. Thump, thump, thump. Inside the town, the viceroy Reason is squabbling with the other leaders about whether to let in God. Reason has become deranged, and he doesn't want to open the gates, even though it would be the rational thing to do, because, well, it's God. You can imagine the speaker bound, gagged, and tied up with rope in some broom closet inside the town. If he weren't bound, he would run out to open the gates. God is like a dashing knight, and the speaker can't wait to rush out into his big, godly arms. We'd better stop before we start swooning...