What does Proverbs 13:18 mean?

The term "reproof" refers to correction, emphasized by the contrast with those who "ignore instruction." Solomon repeatedly warns about the hardships brought on by being hard-headed—by ignoring good advice (Proverbs 1:7; 9:7–12; 12:15). In general, those who refuse to be corrected put themselves on a path to failure. This is partly in terms of their reputation, but also applies to their wealth and employment.

The ability to accept teaching—to "heed reproof"— is an asset in one's education, job performance, and spiritual development. No employer wants to keep an untrainable employee on the company's payroll. No one wants to hire a know-it-all (Proverbs 13:1). Furthermore, by ignoring instruction a person never learns how to accomplish a task, and therefore goes through life as a failure. He disgraces himself in the eyes of those who know him. A person who willingly receives correction and instruction (Proverbs 12:1) performs each task successfully and advances in his employment. His employer is more likely to reward him with praise, or other benefits.

Paul urges Timothy to "preach the word, be ready in season and out of season; reprove, rebuke, and exhort, with complete patience and teaching" (2 Timothy 4:2).