Matthew Poole and continuators on Proverbs 21:15

15 It is joy to the just to do judgment, but destruction shall be to the workers of iniquity.

The sense is either 1. He is highly pleased and delighted with it. Or 2. He reapeth much comfort and benefit by it, which is opposed to the following destruction: joy is put for matter or cause of joy

To do what is just or good, for this is opposed to working of iniquity.

Or, as others render it, terror or horror, opposite to joy.