God’s righteousness means that he rules his creation with impartiality, he punishes the wicked with wrath, he keeps his promises, and he rescues the oppressed. All of these things are right. But they are not the heart of God’s righteousness. They are what God’s righteousness does, but they are not what righteousness is.
In other words, when we’re talking about God’s righteousness and justice, there is something deeper than ruling creation impartially, and judging the wicked, and rescuing the oppressed, and keeping his promises. And we can get at this deeper thing by asking, “How does God know what is right?” Does he have a book that tells him? When he’s deciding on a course of action, does he pull a volume off his shelf and consult it?