preach the good news: The Greek verb here is related to the noun often translated as "gospel" or "good news" (see study note on 2:9–10; see also 1:19; 7:22; Matthew 4:23; 24:14; Mark 1:1, 15; 16:15; Acts 8:4, 12; Romans 1:1–6, 15–17; 10:15–17; Galatians 1:6–9; Ephesians 2:14–18; 3:6–7).
The kingdom of God was the main message of Jesus (see Mark 1:15). God began to show his rule (his kingly authority) through what Jesus said and did.