Then they said to the woman, “Now we believe, not because of what you said, for we ourselves have heard Him and we know that this is indeed the Christ, the Savior of the world.” John 4:42
When the Samaritan woman told others about the Lord Christ Jesus, they first thought that she was telling them the truth, and that is evidenced by the fact that they walked out to meet Him.
When they met Jesus, however, they personally recognized Him as the long-awaited Messiah. Their secondhand belief became firsthand knowledge. They proclaimed, “This is indeed the Christ, the Savior of the world.” The word “world” means the whole cosmos without exceptions. Reading these passages, one must either believe that Jesus is the Savior of the whole world or that He is not. The Bible says the He is, and leaves no middle ground.
From “The Ultimate Reconciliation of All: As Found in 25 Key Passages” by George Howe and Darroll Evans