How do the warnings about correcting scoffers in Proverbs 9:7-9 affect our understanding of Matthew 18:15-20?
"He who corrects a scoffer gets shame for himself, and he who rebukes a wicked man only harms himself. Do not correct a scoffer, lest he hate you; rebuke a wise man, and he will love you. Give instruction to a wise man, and he will be still wiser; teach a just man, and he will increase in learning" (Proverbs 9:7-9)
"Moreover if your brother sins against you, go and tell him his fault between you and him alone. If he hears you, you have gained your brother. But if he will not hear, take with you one or two more, that 'by the mouth of two or three witnesses every word may be established.' And if he refuses to hear them, tell it to the church. But if he refuses even to hear the church, let him be to you like a heathen and a tax collector" (Matthew 18:15-17).
The Hebrew word lets, translated as "scoffers" or "mockers", refer to people who are arrogant in their own knowledge which leads them to foolishly disrespecting the commands of God. "How long, you simple ones, will you love simplicity? For scorners delight in their scorning, and fools hate knowledge" (Proverbs 1:22). Such people are best to be avoided. "Blessed is the man who walks not in the counsel of the ungodly, nor stands in the path of sinners, nor sits in the seat of the scornful" (Psalms 1:1). The problem is that their standard of authority is themselves. There is no way to reason with him.
Matthew 18, however, deals with an unresolved dispute between two brethren. The fact that both parties involved are brothers in Christ generally precludes either one from being a scoffer. I supposed that if you were dealing with a brother who has fallen into the sin of mockery, that Proverbs 9:7-9 will serve as advance warning that the problem will not be easily resolved because the mocker will turn on the one trying to bring him out of his sin.
Proverbs 9:7-9 is similar to Christ's warning, "Do not give what is holy to the dogs; nor cast your pearls before swine, lest they trample them under their feet, and turn and tear you in pieces" (Matthew 7:6). Some people cannot be rescued and attempting to do so will cause you harm.