Albert Barnes Commentary John 4:9

"The Samaritan woman therefore saith unto him, How is it that thou, being a Jew, askest drink of me, who am a Samaritan woman? (For Jews have no dealings with Samaritans.)" — John 4:9 (ASV)

No dealings with the Samaritans. For an account of the Samaritans, and of the differences between them and the Jews, see Barnes on Matthew 10:5.