David
Psalm 66:18BSB·traditional attribution

If I had cherished iniquity in my heart, the Lord would not have listened.

John Calvin Reformed @genevareformer

PSALM 66 There may have been one deliverance in particular, which the Psalmist celebrates here in the name of the Church, but he includes the many and various mercies which God had all along conferred upon his chosen people. While he takes notice of the divine interposition in their behalf, in a crisis of great mercy and distress, he suggests it as matter of comfort...

Commenting on Psalm 66:1-20

C.H. Spurgeon Reformed Baptist @princeofpreachers

If I regard iniquity in my heart. If, having seen it to be there, I continue to gaze upon it without aversion; if I cherish it, have a side glance of love toward it, excuse it, and palliate it; The Lord will not hear me. How can he? Can I desire him to connive at my sin, and accept me while I wilfully cling to any evil way?

Matthew Henry Presbyterian @wholebiblehenry

The psalmist, having before stirred up all people, and all God's people in particular, to bless the Lord, here stirs up himself and engages himself to do it. I. In his devotions to his God, Psa 66:13-15. He had called upon others to sing God's praises and to make a joyful noise with them; but, for himself, his resolutions go further, and he will praise God, 1.

Commenting on Psalm 66:13-20