Let them be as chaff before the wind - As chaff is driven away in winnowing grain. See the notes at Psalms 1:4.
And let the angel of the Lord chase them - Drive them away, or scatter them. Angels are often represented in the Scriptures as agents employed by God in bringing punishment on wicked people. See 2 Kings 19:35; Isaiah 37:36; 1Ch 21:12, 1 Chronicles 21:30; 2 Samuel 24:16.