Psalm 99

On February 3 I am going to be preaching on Psalm 99. I would love to hear what you think about this Psalm. It begins off,

Yahweh reigns,
let the nations tremble

The nations that think they reign should tremble because they don't. For the psalmist it would have been the nations like Egypt or Assyria or Babylon or even that nation of Israel.
What nations today think they reign?
Perhaps we can be more personal. What things think they reign (control) our lives?
What do you think it means that they should tremble?