What does John 3:29 mean?
John the Baptist was clear from the beginning that his ministry was about leading people to Jesus (John 1:23; 3:28). So, when people tell him Jesus is attracting more attention (John 3:26; 4:1), he is not concerned. In fact, he is joyful—this is what God called him to do, and he's seeing it happen.Wedding terminology is common is the Bible. God is often pictured as a groom who takes Israel, or His people, as a bride (Isaiah 54:4; Jeremiah 2:2; Hosea 2:19). The best man at a wedding is not meant to be the center of attention. Of all the men involved in the wedding, the groom is supposed to get all the applause. The best man's role is to help the groom, to be his advocate, and his friend. When the groom has his bride, the best man is joyful. He's not jealous or angry, because that outcome is exactly what he wanted in the first place.
In this way, John the Baptist has acted like a best man for Jesus. Now that Jesus has come on the scene, the Baptist is happy to see Him succeed. Next, the Baptist explains the logical result of this change (John 3:30). If people are going to wholeheartedly follow Jesus, they can't split their attention to stay with the Baptist, as well. For the Baptist's mission to succeed, he must lose popularity and fame, and Jesus must gain it.