cleanseth away. is cleansing. Supply the Ellipsis (App-6), "[though it be] an evil".
evil. Hebrew. ra'a'. App-44.
belly. Supply the Ellipsis from preceding clause, "[though they be an evil]"
Related Commentaries of Proverbs 20:30
Proverbs 20:30
30 The blueness of a wound cleansethi away evil: so do stripes the inward parts of the belly.