Charles Ellicott Commentary Psalms 40:9

"I have proclaimed glad tidings of righteousness in the great assembly; Lo, I will not refrain my lips, O Jehovah, thou knowest." — Psalms 40:9 (ASV)

I have preached. —Literally, I have made faces glad.

Notice the rapid succession of clauses, like successive wave-beats of praise, better than any elaborate description to represent the feelings of one whose life was a thanksgiving.