Therefore the LORD waits to be gracious to you, and therefore He exalts Himself to show mercy to you. For the LORD is a God of justice; blessed are all those who wait for Him.
The Lord waits.
He wants to be gracious to you and to me and if He acted before He waited, He would have to destroy us all.
But He exalts Himself in His mercy to us.
He is a God of justice, yet His desire is to be gracious and merciful, so He waits.
He waits so that we might respond to His mercy and in turn, wait for Him.