I will love thee, O LORD, my strength.
The time was the close of David's life. (2 Samuel 22:1-51; 2 Samuel 23:1-39.) The varied form in 2 Samuel 22:1-51, which omits the words "to the chief Musician," was subsequent to the form here, which was for liturgical use in the sanctuary. The psalm is 'a great Hallelujah, with which David retires from the theater of life,' praising God for all past deliverances. Compare with the title, Moses' song, Deuteronomy 31:30; also Exodus 15:1.
The servant of the Lord - a title of dignity, not mere humility (Psalms 18:50). David was the first after Moses and Joshua specially so called, having 'for the good of his own generation served the will of God' (Acts 13:36, Greek).
Delivered ... from ... all his enemies, and ... Saul. In the case of Saul he was but a private man assailed by a powerful king: hence, in Psalms 18:4-19 he appears as passive, drawn out of the floods of his strong enemy's hostility by the Almighty. But in his deliverance from later enemies (Psalms 18:28-45), he appears as an active and triumphant warrior.
Psalms 18:1-50.-The theme (Psalms 18:1-3); his earlier distresses, and deliverance, in answer to his cry, by the Almighty (Psalms 18:4-19); the ground of his being heard, his righteousness (Psalms 18:20-27); the aid which God gave him against foreign foes when he had become king, and would still give (Psalms 18:28-45) conclusion, renewed praise for God's past grace, and His promised grace to David's seed forever (Psalms 18:46-50).
I will love thee, O Lord - Hebrew, love with intense affection х raacham (H7355), to love from the inmost bowels: a word made by David, as no existing term was strong enough to express his feeling (Jeremiah 31:20); splangchnizomai (G4697), from splangchna (G4698)]. The love of God experienced so richly by David generated in him an intense reciprocal love toward God.
My strength - who suppliest me with both external and internal strength. Compare 1 Samuel 30:6, end.