Albert Barnes Commentary John 4:39-42

"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. So when the Samaritans came unto him, they besought him to abide with them: and he abode there two days. And many more believed because of his word; and they said to the woman, Now we believe, not because of thy speaking: for we have heard for ourselves, and know that this is indeed the Saviour of the world." — John 4:39-42 (ASV)

And many of the Samaritans of that city believed on him, and so on. There is seldom an instance of so remarkable success as this. From a single conversation, in circumstances, in a place, and with an individual unlikely to produce such results, many sinners were converted; many believed on the testimony of the woman; many more came to hear, and believed because they heard him themselves.

We should never despair of doing good in the most unpromising circumstances, and we should seize upon every opportunity to converse with sinners on the great subject of their souls' salvation.