Proverbs 20:30 - Joseph Benson’s Commentary on the Old and New Testaments

The blueness of a wound cleanseth away evil Grievous wounds which make men black and blue, or severe punishments, are the means which are frequently most effectual to reclaim a wicked man, and to purge out his corruptions; so do stripes Hebrew, ומכות, and stripes, which answer to wounds in the former clause; the inward parts of the belly Hebrew, חדרי בשׂן, literally, the chambers of the belly, that is, the inward recesses of the mind. The sense of the whole is, Grievous wounds, or stripes, cleanse not only the outward man, by keeping it from evil actions, but even the inward man, by expelling or subduing vile affections; which is a great and blessed benefit of afflictions.