Chapter 18 is an interesting one; it seems to have a theme loosely structured by friends and foes. This develops quickly in the first four verses:

An unfriendly person pursues selfish ends
    and against all sound judgment starts quarrels.

Fools find no pleasure in understanding
    but delight in airing their own opinions.

When wickedness comes, so does contempt,
    and with shame comes reproach.

The words of the mouth are deep waters,
    but the fountain of wisdom is a rushing stream.

Proverbs 18:1-4

V. 1: Selfish and self-centered people isolate themselves from others. A self-centered person is conceited to the point that he goes into a rage against the sound words and advice of others. This is true in the Christian community also (i.e. Romans 16: 17,18).

V. 2: A fool does not like to take in, to learn, but only to talk. Facts, figures, and business have no interest for the fool-only to talk, talk, talk, and he really has nothing to say that is worth listening to.

V. 3: A Hebrew parallelism, paralleling “wicked” and “shame” and paralleling “contempt” and “reproach”. The wicked loses a good name and turns critic of all that is good and of all who are good. “When wickedness comes,” watch out! He injects contempt and reproach into the association. The rule is, those who deserve no honor themselves are sure to dishonor all others, and those who themselves are good are the last to suspect others of evil.  

V. 4: The verse is not talking about just any mouth but the mouth of “wisdom”. A wise man’s mouth is likened to a “deep”, “flowing” spring. Such is a great blessing to all around him, and to such they turn for counsel and guidance.

It is not good to be partial to the wicked
    and so deprive the innocent of justice.

The lips of fools bring them strife,
    and their mouths invite a beating.

The mouths of fools are their undoing,
    and their lips are a snare to their very lives.

The words of a gossip are like choice morsels;
    they go down to the inmost parts.

Proverbs 18:5-8

V. 5: Here we have a verse dealing with legal matters. We must not take a person’s wealth, fame or position into account in a legal case before a court. Many passages teach the same: Lev. 19:16; Deut, 1:17; 16:19; Prov. 24:23; 28:21. A nation’s principles are either maintained or corrupted by its judicial officials.

V. 6: A fool’s lips show that he is a fool. He says the wrong thing or speaks at the wrong time, or he says what he does in the wrong place or to the wrong person. He is like a child who does not know these wise details of speech. Consequently, he gets himself into trouble with others, and his superiors correct him severely for it.

V. 7. This verse continues the topic of v. 6. Similar passages: Prov. 10:14; 12:13; 13:3; Eccl. 10:12. The fact that such behavior can imperil a person’s very life, shows the serious destruction that his speech can bring. This saying is carried twice in Proverbs (see 26:22 also), probably for a needed emphasis.

V. 8: A “gossip” is one who goes behind people’s backs in talking about them, saying things that are not in the best interests of the one being spoken about. The verse brings out the sad fact that people are willing to listen to such cowardly, wrong, ruinous talk (They are as “choice morsels”). They are swallowed without question (“they go down to the inmost parts”).