20:6 David was confident he would be successful in the coming conflict because he was the Lord's anointed. Of course, if David had been guilty of sin God might not have given him the victory. However the king believed that he was clean and with the intercession of his people he felt even more certain that he would emerge the victor.
20:7 He repudiated confidence in the most sophisticated physical implements of warfare available but affirmed his reliance on the Lord Himself for victory (cf. Exod. 14; Judg. 4). The name of the Lord refers to His character, reputation, and nature. David gained confidence as he meditated on his God.
20:8 The king was sure of success. Often in the psalms the writers expressed strong confidence by describing an event yet future as already having taken place with the desired result as here.