John Calvin Commentary Psalms 7:10

"My shield is with God, Who saveth the upright in heart." — Psalms 7:10 (ASV)

My shield It is not surprising that David often mixes meditations with his prayers, in order to inspire himself with true confidence. We may go to God in prayer with great eagerness; but our fervor, if it does not gather new strength, either immediately fails or begins to diminish.

David, therefore, to continue in prayer with the same ardor of devotion and affection with which he began, recalls some of the most common truths of religion, and in this way fosters and invigorates his faith. He declares that as God saves the upright in heart, he is perfectly safe under his protection.

From this it follows that he had the testimony of an approving conscience. And, as he does not simply say the righteous, but the upright in heart, he appears to have in mind that inward searching of the heart and reins mentioned in the preceding verse.