John Calvin Commentary John 4:39

"And from that city many of the Samaritans believed on him because of the word of the woman, who testified, He told me all things that [ever] I did." — John 4:39 (ASV)

And many Samaritans out of that city believed. The Evangelist here relates the success of the woman’s announcement to her citizens, from which it is evident that the expectation and desire for the promised Messiah had no small vigor among them. Now, the word believe is used here imprecisely, meaning that they were induced by the woman’s statement to acknowledge Christ as a Prophet. This is, in some respects, a beginning of faith, when minds are prepared to receive the doctrine.

Such an entrance to faith receives here the honorable designation of faith, to inform us how highly God esteems reverence for His word, when He confers so great an honor on the receptiveness of those who have not yet been taught. Now, their faith manifests itself in this: they are seized with a desire to benefit, and for that reason, they desire that Christ should remain with them.