The psalmist’s back is against the wall. He has faced God, he has asked God for rescue, and he has appealed to his own integrity — that’s 119:153. In v. 154 there is a subtle, revealing development.
“Plead/defend my cause and redeem me” is largely the same as 153a — he faces God, he asks God to redeem (or rescue) him. But notice the following:
“Give me life according to your promise” (154b).
Rescuing and redeeming is understood as “life.”
More importantly, instead of appealing to his own integrity, as he does in 153b, in 154b he asks God to preserve his life “according to your promise.” The uttered word of God, the promise that God would be Israel’s God (as Israel remained faithful), is the foundation of his longing for life.
Covenant faithfulness is what he appeals to with God. He thinks his life should be preserved in order to demonstrate to the world that God is faithful to his covenant words of promise.
Are we this theological? This protective of God’s glory? This protective of God’s reputation? This protective of God’s covenant words of promise? Do we want deliverance in order to bring glory to God or to save our own skin?