Psalm 59:13 (ESV)

13 consume them in wrath; consume them till they are no more, that they may know that God rules over Jacob to the ends of the earth. Selah

Keep in mind that this is still a prayer—and certainly not a personal exercise in revenge. How much love is David showing to Saul who tried to kill him numerous times. David’s farewell song to Saul and Jonathan is especially heartbreaking (2 Samuel 1:17–27 and especially 2 Samuel 1:23 Saul and Jonathan, beloved and lovely…). A Christian is called to follow Jesus, see 1 Peter 2:21.

This is still prayer language: consume them in your wrath; consume them so that they no longer exist. As they are being disciplined, it must occur to them: God is the King of Jacob and reigns until the ends of the earth. And let us keep in mind, when reading this Psalm, that this not only applies to the time of David. No, the point is that God’s justice applies to the whole earth. God’s righteousness must be known by all the nations on earth (see Psalm 59:5 punish all the nations).

You may pray to be delivered from injustice; also that the enemies will be inhibited in their sinful actions; and at the same time that God’s kingdom will be promoted. In 1 Samuel 2:10 we read Hannah’s prayer (the transition from Judges to Kings) where she says, “The adversaries of the Lord shall be broken to pieces; against them he will thunder in heaven. The Lord will judge the ends of the earth; he will give strength to his king and exalt the horn of his anointed.” In Psalm 92:9–15 we read that God’s enemies stand over against God’s righteousness (Psalm 92:15). Lastly, in Psalm 58:10–11 it says, surely there is a God who judges on earth.

Also, reject the idea that the Old Testament is harsh and the New Testament more friendly and loving. This does not make sense. 1 Corinthians 16:22 reads, If anyone has no love for the Lord, let him be accursed. Further, we read in Galatians 1:9, If anyone is preaching to you a gospel contrary to the one you received, let him be accursed. And lastly, 2 Thessalonians 1:6–9a says, “…indeed God considers it just to repay with affliction those who afflict you, and to grant relief to you who are afflicted as well as to us, when the Lord Jesus is revealed from heaven with his mighty angels in flaming fire, inflicting vengeance on those who do not know God and on those who do not obey the gospel of our Lord Jesus. They will suffer the punishment of eternal destruction, away from the presence of the Lord…” And we can add many more passages from the New Testament on this topic.