Psalms 18:20

Here, I. David reflects with comfort upon his own integrity, and rejoices in the testimony of his conscience that he had had his conversation in godly sincerity and not with fleshly wisdom, Co2 1:12. His deliverances were an evidence of this, and this was the great comfort of his deliverances. His enemies had misrepresented him, and perhaps, when his troubles continued long, he began to suspect himself; but, when God visibly took his part, he had both the credit and the comfort of his righteousness. 1. His deliverances cleared his innocency before men, and acquitted him from those crimes which he was falsely accused of. This he calls rewarding him according to his righteousness (Psa 18:20, Psa 18:24), that is, determining the controversy between him and his enemies, according to the justice of his cause and the cleanness of his hands, from that sedition, treason, and rebellion, with which he was charged. He had often appealed to God concerning his innocency; and now God had given judgment upon the appeal (as he always will) according to equity. 2. They confirmed the testimony of his own conscience for him, which he here reviews with a great deal of pleasure, Psa 18:21-23. His own heart knows, and is ready to attest it, (1.) That he had kept firmly to his duty, and had not departed, not wickedly, not wilfully departed, from his God.

— Matthew Henry's Concise Commentary (public domain)

The statements of innocence, righteousness, &c., refer, doubtless, to his personal and official conduct and his purposes, during all the trials to which he was subjected in Saul's persecutions and Absalom's rebellions, as well as the various wars in which he had been engaged as the head and defender of God's Church and people.

— Jamieson-Fausset-Brown Commentary (public domain)