John Gill's Exposition of the Whole Bible
Proverbs 21:15
[It is] joy to the, last to do judgment,.... It is with pleasure he does it; he delights in the law of God, after the inward man, and finds much peace of mind and joy in the Holy Ghost in keeping it, and observing its commands, which are holy, just, and good; yea, it gives him pleasure to see justice done by others; both by private persons in their dealings with one another; and especially by judges putting the laws in execution, as their office requires; whereby much good comes to a nation in general, and to particular persons;
but destruction [shall be] to the workers of iniquity; that make a trade of sinning; whose whole life is a continued series of sin and iniquity; who take much pains in committing sin, and are constant at it; everlasting destruction is in their ways, and they lead unto it: or, "terror" a shall be to them; terror of mind now at times, in opposition to the joy and peace a good man finds; and dreadful horror at death and to all eternity: or, as it is joy to a just man to see public justice done, and good laws put in execution, it is a terror to evildoers, Romans 13:3.
a מחתה "pavor", V. L. "horror", Tigurine version; "terror", Vatablus, Mercerus; "consternatio", Cocceius, Michaelis, Schultens.