Jaron's prayer is tame compared to the psalmists. Consider Psalms 139:19–22,
O that You would slay the wicked, O God; Depart from me, therefore, men of bloodshed. For they speak against You wickedly, And Your enemies take Your name in vain. Do I not hate those who hate You, O LORD? And do I not loathe those who rise up against You? I hate them with the utmost hatred; They have become my enemies.
Or again, Psalm 69: 22-28,
Let their table before them become a snare; And when they are in peace, let it become a trap. Let their eyes be darkened, so that they cannot see; And make their loins continually to shake. Pour out thine indignation upon them, And let the fierceness of thine anger overtake them. Let their habitation be desolate; Let none dwell in their tents. For they persecute him whom thou hast smitten; And they tell of the sorrow of those whom thou hast wounded. Add iniquity unto their iniquity; And let them not come into thy righteousness. Let them be blotted out of the book of life, And not be written with the righteous.Squirming yet? One more then. Psalm 109:6-15,
Appoint a wicked man against him; let an accuser stand at his right hand. When he is tried, let him come forth guilty; let his prayer be counted as sin! May his days be few; may another take his office! May his children be fatherless and his wife a widow! May his children wander about and beg, seeking food far from the ruins they inhabit! May the creditor seize all that he has; may strangers plunder the fruits of his toil! Let there be none to extend kindness to him, nor any to pity his fatherless children! May his posterity be cut off; may his name be blotted out in the second generation! May the iniquity of his fathers be remembered before the Lord, and let not the sin of his mother be blotted out! Let them be before the Lord continually, that he may cut off the memory of them from the earth!Bitter much?
Some look at these and believe they are below the dignity of Christian Scripture, that they conflict with the ethic of the rest of the Bible, especially as taught and modeled by Jesus. But do they? What are we to make of these. Without much elaboration, here's a few points to consider.
1. Some have tried to explain these passages using the prescriptive vs. descriptive distinction. In other words, the psalmist is describing truthfully what lies in his hears, and it ain't pretty. This is a long way from saying the Bible condones such attitudes, let alone commands or prescribes them. However, I don't think this is an adequate approach. For one, we are never given any indication of God's disapproval of such prayers. (BTW, you see such imprecations in the New Testament as well, though not as frequent. Consider what Paul says in 1 Corinthians 16:22, "If anyone does not love the Lord, let him be accursed." Look also at Luke 10:10-16; Gal 1:8; 5:12; 2 Thess 1:6-10; 2 Tim 4:14; Rev 6:10; 19:1-2). Harry Mennega has pointed out that "the New Testament appears not in the least embarrassed with the Old Testament imprecations; on the contrary, it quotes freely from them as authoritative statements with which to support an argument. The New Testament not only quotes passages which, though themselves not imprecations, are found in a Psalm with an imprecatory section; but also, and this is more remarkable, it quotes with approval the imprecations themselves."
2. Also, I'm sure most of us have prayed, without realizing it maybe, such imprecations. Oh, we're not as detailed, but we pray "Maranatha, Come Lord Jesus." We pray, "Let your kingdom come, let y our will be done." It seems abundantly clear from Scripture that the return of Jesus and the final establishment of the kingdom will mean judgment for untold millions. And we pray for it (and we should).
3. John Piper urges us to "Consider that, in some of these psalms, love for the enemy has been pursued for a long time. 'They requite me evil for good. . . . When they were sick, I wore sackcloth' (Ps. 35:12-13). 'In return for my love they accuse me, even as I make prayer for them. So they reward me evil for good, and hatred for my love' (Ps. 109:4-5)."
4. Sam Storms offers this good observation, "These prayers are not expressions of personal vengeance. In fact, most imprecations are in psalms written by David, perhaps the least vengeful man in the OT (consider his dealings with Saul, Nabal, Absalom, Shimei, etc.; see especially 2 Sam. 24:12). David never asks that he be allowed to “get even” with or “pay back” his enemies. His prayer is that God would act justly in dealing with transgressors. There is a vast difference between vindication and vindictiveness. David’s passion was for the triumph of divine justice, not the satisfaction of personal malice. The OT was as much opposed to seeking personal vengeance against one's personal enemies as is the NT (see Exod. 23:4-5; Lev. 19:17-18)." In essence, the impreccatory prayers are good examples of giving over to God injustice and asking him to judge, to make right. It's David's (or others) refusing to pursue revenge, acknowledging "Vengeance is mine, saith the Lord" (Romans 12:9. I just went all King James).
5. Moreover, we ought to recognize that these impreccatory psalms are simply claiming the promises of God. He has promised to fight for his people, to do justice, to punish the wicked, etc. This is simply asking God to do what he has promised to do.
6. Lastly, the impreccatory psalms express moral repugnance at sin and evil, not simply personal dislike of a person (in fact, rarely are the impreccatory psalms offered against a specific person, but a class of people, i.e. "those who hate the Lord", "the wicked", etc.). Ultimately, the motivation is the vindication of God's righteousness and glory, not personal revenge.
Now, my caveat. I don't trust myself to sort out my self-centered, unholy motives from my noble, holy ones. So, I won't pray impreccatory psalms over specific people. But, the broad categories are appropriate, even if I'm praying in the same prayer, "Father, forgive them and bring them to the grace of repentance."
In case you want to read more imprecations, here's a more full list: Pss. 5:10; 6:10; 7:6; 9:19-20; 10:2,15; 17:13; 28:4; 31:17-18; 35:1,4-8,19,24-26; 40:14-15; 41:10; 54:5; 55:9,15; 56:7; 58:6-10; 59:5,11-14; 63:9-10; 68:1-2; 69:22-28; 70:2-3; 71:13; 79:6,10-12; 83:9-18 (cf. Judges 4:15-21; 5:25-27); Pss. 94:1-4; 97:7; 104:35; 109:6-19,29; 119:84; 129:5-7; 137:7-9; 139:19-22; 140:8-11; 141:10; 143:12.