Psalms 9:1
1I will give thanks to the LORD with my whole heart. I will tell of all your marvelous works.
Wesley’s frame for the psalm: David praises God for victory over enemies (vv. 1–6), triumphs in confidence that God will judge the world and protect his people (vv. 7–10), calls others to praise (vv. 11–12), and prays for help (vv. 13–20).
Whole-heart thanksgiving is a sincere act—recounting deeds already done so the heart stays grateful and open. Grace enables praise; the pray-er must still give thanks with the whole heart, not half-lips and half-boast.
Calvin: David begins thus to induce God to succor him in present calamities. Past mercies should inspire confidence that God will be gracious in what comes. The whole heart means an upright, sincere heart opposed to a double heart—distinguishing him from hypocrites who praise with lips while hearts are unaffected. Whatever commendable in him proceeded entirely from pure grace. Worldly victors steal glory back to their own valor; David will not.
Whole-heart praise is grace-wrought sincerity that refuses to split glory with self. Remembered marvels open the gate of prayer.