Psalms 66:18 - Joseph Benson’s Commentary on the Old and New Testaments

If I regard iniquity in my heart, &c. God's hearing and granting my petitions hath brought along with it a testimony of my sincerity in serving him, far more valuable than my kingdom; for, if I had been guilty of known iniquity, or had entertained in my heart a desire or intention to commit it, the Lord, who hates iniquity, would have denied my request. What the psalmist here observes merits our deep attention. From this, and many other passages in the Old Testament, we learn that the religion of the Holy Scriptures has always been the same in substance, and that in the time when various sacrifices and divers ceremonies were enjoined, the truly pious were persuaded that sincerity of heart and purity of intention, with a conscientious care to abstain from all known sin, were things absolutely necessary in order to their pleasing God, and being acceptable in his sight: and that without these, thousands of sacrifices and burnt-offerings, and the most scrupulous observance of outward ceremonies, were of no signification before him who searches the heart, and requires truth in the inward parts.