This is the first Psalm in which David has not been mentioned in the heading since Psalm 50.
66:1-12 is a national thanksgiving
66:1-4 All the earth is to praise God
66:5-7 God turned the sea into dry land
66:8-12 God has afflicted HIs people but finally brought them to a place of abundance
66:13-20 is an individual thanksgiving
66:13-15 He pays his vows to God
66:16-20 He gives thanks to God
How does the Psalm speak of Jesus?