The blueness of a wound cleanseth away evil: so do stripes the inward parts of the belly.
– Proverbs 20:30
Foolishness invites physical punishments and often requires them to be delivered from folly (Proverbs 7:22; 10:13; 17:10; 19:29; 26:3). The inward parts of the belly refers to the inner being of man, and especially his conscience. The general tenor of Proverbs is that wisdom is imparted in a progressive way through words, instruction, reproof, the example of the rod, and the experience of the rod. The most obstinate will not receive any of these and turn from folly, and therefore ends in destruction (Proverbs 6:15; 15:10; 29:1). To put the proverb in modern terms: there is always a hard way to learn.