What does John 3:25 mean?

John uses the plural term "the Jews" to refer to local religious leaders, such as the Pharisees. This argument is between followers of John the Baptist and a particular one of those leaders. The Greek term here is singular, so this is a debate with a single person. That person is unnamed, but it could be Nicodemus. He had approached Jesus alone, at night, to speak with Him about His teachings (John 3:1). Most of that discussion was about rebirth and salvation. Here, the discussion is over "purification," closely related to baptism.

The word used to refer to this "dispute" is zētēsis, which implies ideas controversy, questioning, and debate. Perhaps this leader confronted the followers of John the Baptist with Jesus' comments about baptism, or with his own interpretation. The fact that there was a debate doesn't necessarily mean that the "argument" was hostile. At the same time, the terms in older manuscripts switch from singular here to plural in the next verse (John 3:26). A possible reason would be that "they," mentioned in the next statement, means other religious leaders. If they heard about the controversy, they might have come to fan the flames. So, this incident may have turned into a deliberate attempt to inspire a rivalry between the Baptist and Jesus.

On the other hand, the "they" of verse 26 may be a reference to the followers of John the Baptist. Perhaps some were jealous of Jesus' success. In either case, the Baptist will set everyone straight.