What does Proverbs 28:21 mean?

Right judgment can include distinguishing between persons, but only on a fair and reasoned basis. "Partiality," in this context, is giving unfair preference to one person over another. A common example is giving more respect to a rich man over a poor one (James 2:1–4). It's never moral to act unfairly. The Book of Proverbs refers to something "not good" several times, about half of which explicitly condemn unfairness in judgment (Proverbs 17:26; 18:5; 24:23). Unfortunately, human beings are prone to corruption. This proverb notes that some will act immorally for a trivial reward, represented by a piece of bread.

The Lord God shows no partiality (Acts 10:34). He loves the whole world of human beings (John 3:16). John chapter 4 records a conversation between Jesus and a Samaritan woman. She was surprised that Jesus, a Jew, would speak to her, because the Jews avoided all contact with Samaritans (John 4:9). After His resurrection, Jesus commissioned the apostles to proclaim the good news of salvation to all people in all places (Acts 1:8). The apostle James chides his readers for discriminating between the rich and poor. He writes: "If you really fulfill the royal law according to the Scripture, 'You shall love your neighbor as yourself,' you are doing well. But if you show partiality, you are committing sin…" (James 2:8–9).