And what can David say more unto thee? for thou, Lord GOD, knowest thy servant.

Wesley's Notes

7:20 David say - Either in a way of gratitude and praise, words cannot express my obligations to thee, nor my sense of these obligations: Or in a way of prayer. What can I ask of thee more than thou hast freely done? Thou knowest - Thou knowest my deep sense of thy favours, and my obligations to thee. And my condition and necessities, what I do or may need hereafter; and as thou knowest this, so I doubt not thou wilt supply me.

Jamieson-Fausset-Brown Bible Commentary

20. what can David say more unto thee?-that is, my obligations are greater than I can express.

Matthew Henry's Concise Commentary

7:18-29 David's prayer is full of the breathings of devout affection toward God. He had low thoughts of his own merits. All we have, must be looked upon as Divine gifts. He speaks very highly and honourably of the Lord's favours to him. Considering what the character and condition of man is, we may be amazed that God should deal with him as he does. The promise of Christ includes all; if the Lord God be ours, what more can we ask, or think of? Eph 3:20. He knows us better than we know ourselves; therefore let us be satisfied with what he has done for us. What can we say more for ourselves in our prayers, than God has said for us in his promises? David ascribes all to the free grace of God. Both the great things He had done for him, and the great things He had made known to him. All was for his word's sake, that is, for the sake of Christ the eternal Word. Many, when they go to pray, have their hearts to seek, but David's heart was found, that is, it was fixed; gathered in from its wanderings, entirely engaged to the duty, and employed in it. That prayer which is from the tongue only, will not please God; it must be found in the heart; that must be lifted up and poured out before God. He builds his faith, and hopes to speed, upon the sureness of God's promise. David prays for the performance of the promise. With God, saying and doing are not two things, as they often are with men; God will do as he hath said. The promises of God are not made to us by name, as to David, but they belong to all who believe in Jesus Christ, and plead them in his name.