Albert Barnes Commentary Psalms 40:10

"I have not hid thy righteousness within my heart; I have declared thy faithfulness and thy salvation; I have not concealed thy lovingkindness and thy truth from the great assembly." — Psalms 40:10 (ASV)

I have not hid thy righteousness within my heart - The word “righteousness” here may denote the divine views on the subject of righteousness, or the divine method of making man righteous; that is, the method of justification, as the word is used in the New Testament (Romans 1:17).

The word, as it might have been used by David, would have been employed in the former sense, as meaning that, knowing what God requires of men, he had not concealed that in his heart or kept it to himself. As used by the Messiah, as I suppose it to be here, it would be employed in the latter sense, or perhaps embrace both.

The idea would be that he had not concealed in his own mind, or kept to himself, the knowledge which he had of the requirements of the law of God, or of the way in which man can be justified or regarded and treated as righteous in his sight. He had fully communicated this knowledge to others.

It is not necessary to say that this was literally fulfilled in the work of the Redeemer. He spent his life making known the great truths about the righteousness of God; he died that he might disclose to man a way by which God could consistently regard and treat men as righteous (Romans 3:24–26).

I have declared thy faithfulness - Your truthfulness; I have shown that God is worthy of confidence. And thy salvation. Your method of salvation, or of saving men.

I have not concealed thy loving kindness - Your mercy or your merciful disposition toward men. He had shown to the human race that God was a merciful Being; a Being who would pardon sin.

And thy truth - The truth which you have revealed; the truth on all subjects which it was important for men to understand.

From the great congregation - That is, as in Psalms 40:9, the assembled multitudes - the throngs that gathered to hear the words of the Great Teacher (Matthew 13:2; Luke 8:4).