The Psalms are often described as a hymnbook or prayer book for God’s people. Yet any reader of the Psalms can’t get far into the book without needing to ask a fundamental question: Are these prayers still fitting for God’s people who live after the cross and the teaching of Jesus? C. John Collins states the matter like this:
Many psalms call on God for help as the faithful are threatened with harm from enemies. In a number of places, the form of the requested help is God’s punishment of these enemies. Christians, with the teaching and example of Jesus (e.g., Matt. 5:38–48; Luke 23:34; 1 Pet. 2:19–23; cf. Acts 7:6), wonder what to make of such curses. How can it possibly be right for God’s people to pray in this way?
Collins’s answer is surprisingly thorough for how concise it is. I encourage you to see what he has to say.