The woman was surprised that a Jewish man would ask her for anything. John explains why: "the Jews have no dealings with the Samaritans" (John 4:9). Matthew Henry says there was "great hatred between the Samaritans and the Jews," and that she was surprised because Jesus did not show the anger of His nation against Samaritans. Gill reads her tone more sharply, saying she asked "in a scoffing, jeering way," and that she might have known He was a Jew "by his language and his dress." Either way, her question points to the wall between them and asks why He is stepping over it.

Jesus did not argue about the divide between Jews and Samaritans. He turned the conversation to what she did not yet know: "If thou knewest the gift of God, and who it is that saith to thee, Give me to drink; thou wouldest have asked of him, and he would have given thee living water" (John 4:10). The one asking for water was really the one who had water to give. Her next questions follow from this (John 4:11-12).

The phrase "have no dealings with" translates sugchraomai, which Thayer defines as "to associate with, to have dealings with." It appears only here in the New Testament. Gill explains the limits of that separation: Jews "might go into their cities and buy food of them, as the disciples did" (John 4:8), but they would not eat at a Samaritan's table, and, as Gill puts it following Dr. Lightfoot, they "refused to receive the least favour or kindness at the hand of a Samaritan."

That is why a simple request for a drink was so surprising. Barnes refers readers to his notes on Matthew 10:5 for the history of the Samaritans and their differences with the Jews.

This question shows Jesus crossing a line His own people kept. He was tired and thirsty (John 4:6-7), and He let Himself need something from a Samaritan woman. That simple request opened a conversation that led to many Samaritans believing in Him as "the Saviour of the world" (John 4:39-42).

The rest of the New Testament shows how deep the divide ran. A Samaritan village would not receive Jesus (Luke 9:52-53), and His opponents later used "thou art a Samaritan" as an insult (John 8:48). Yet Jesus met this woman at the well and offered her "the gift of God" (John 4:10). His grace was not limited by the walls people built.