What does John 4:42 mean?
The first thing that brought these people to hear from Jesus was the Samaritan woman's testimony (John 4:29–30). This is remarkable enough, in that a woman's testimony was not usually respected in that era. Her reference to Jesus' deep knowledge of her past, and the fact that this past might have involved many of the men in town (John 4:17–18) probably added to their motivation. All the same, it was her willingness to act in faith which started the revival in her community (John 4:39).Once a few people had met Jesus, they invited Him to spend additional time in town (John 4:40). This gave many more opportunities for Jesus to teach and preach. As one would expect, this was even more effective than a brief conversation. Whatever the people of town had thought about Jesus, based on the claims of the Samaritan woman, they now had personal, first-hand confirmation.
Jesus has travelled with His disciples from Jerusalem into Judea and now into Samaria. The statement about Jesus being the "Savior of the world" is not only true, but also meant to be a lesson to the disciples. After His resurrection, and just prior to ascending to heaven, Jesus will instruct His disciples. His command then will be to "be [His] witnesses in Jerusalem and in all Judea and Samaria, and to the end of the earth" (Acts 1:8). What He will ask them to do, He has already done by example.