Psalms 109:27

That they may know that this is thy hand; that thou, LORD, hast done it.

Psalm 109:27 belongs to an imprecatory psalm that foretells God's retributive wrath upon evildoers. Its words are God's inspired declaration of the punishments awaiting the wicked, not David's personal prayer for vengeance. The outcomes it sets forth are God's own work.

Those who plot wickedness against the innocent receive the fruit of their own wrongdoing, receiving back the very consequences they intended for others. The verse belongs to a plea for divine justice in which that reversal takes place. It prays that God's deliverance will make His hand and action unmistakable, so that people will recognize and know that the Lord Himself has acted and done it.