Albert Barnes 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 righteousness in the great congregation - I have maintained and defended the principles of righteousness and truth among assembled multitudes. It would be difficult to see how this could be applied to David himself, or on what occasion of his life this could be said of him; but no one can doubt that this is applicable to the Messiah:

• He was a preacher.
• He addressed vast multitudes.
• Before them all, and at all times, he maintained and illustrated the great principles of righteousness as demanded by the law of God, and unfolded the way in which all those multitudes might become righteous before God.

Lo, I have not refrained my lips - I have not closed my lips. I have not kept back the truth.

O Lord, thou knowest - He could make this solemn appeal to God as the Searcher of hearts, in proof that he had faithfully uttered all that had been required of him in making known the will of God. Compare John 17:4, John 17:6, John 17:8, John 17:14, John 17:26.