"Blows that wound cleanse away evil; strokes make clean the innermost parts" (Proverbs 20:30 RSV).
This is a challenging passage to address. It clearly means what it says: Harsh punishment is necessary to cleanse someone of evil. Some translations read 'Blue wounds cleanse away evil," which is pretty much the same thing, describing wounds so severe that they leave welts.
This passage, and others like it, have been used throughout history to justify the beating of slaves, children, wives, and others. It's an example of how a literal reading of the Bible without a recognition of its progressive nature can be extremely dangerous. Certainly corporal punishment has been used and justified throughout history but, as Jesus taught consistently, we are called to a higher, more loving understanding. 'You have heard it said ... but I say to you' is one of his favorite teaching methods.
The Book of Proverbs is a collection of adages and teachings with no particular author, structure, or purpose. It, like much of the Hebrew scriptures, is an expression of an understanding of God as a severe ruler who does not hesitate to punish disobedience. Jesus teaches a God of infinite love rewarding our every creative, loving choice. It's a question of living in fear of God or love of God. Certainly there is a need for discipline in resisting our fear-based thoughts; the process isn't easy. But it can be done in love if we lift our consciousness to the level that Jesus calls us to.