‘Answer me when I call, O God of my righteousness,
You have set me at large when I was in distress.
Have mercy on me and hear my prayer.'
The psalm begins with prayer. The writer is grateful that when he was in distress God delivered him from it and set him ‘at large'. He had brought him out of his distress both physically and spiritually and given him freedom, both outwardly and within himself. This would well fit the fact that David was now delivered from the initial source of impending danger. Now he prays for continued mercy to be shown to him, in response to his praying.
‘O God of my righteousness.' The righteous God is the source of his vindication, and its upholder. It is the righteous God Who has accepted him as righteous through forgiveness, and enables him to walk in righteousness. Thus his conscience can be clear because of God's graciousness.
The Christian has an equally great joy. He can say that Christ has been made to him righteousness, that we have been ‘made the righteousness of God in Him' (1 Corinthians 1:30; 2 Corinthians 5:21).
‘Have mercy on me.' This is meant in the sense of ‘show your graciousness towards me' (see Exodus 34:6). He is seeking that God will continue to act on his behalf in response to his prayer.