John Lightfoot on John 4:9

[For the Jews have no dealings with the Samaritans.] I. That translation, the Jews have no dealings with the Samaritans, which the French and English follow, seems to stretch the sense of the word beyond what it will well bear: for, 1. Granting the Samaritans were mere heathens, (which some of the Rabbins have affirmed,) yet did not this forbid the Jews having any kind of dealings with them; for they did not refuse merchandising with any of the Gentile nations whatever. See Nehemiah 13:16, &c. 2. But if the Samaritans were true proselytes, as R. Akibah asserts, or 'as the Israelites in all things,' as Rabban Simeon Ben Gamaliel saith of them; then much more might the Jews have dealing with them.

II. "It is lawful to eat the unleavened bread of the Samaritans, nor is there any suspicion as to their leavened bread neither. This is to be understood, if the Samaritan should knead it in the house of an Israelite." Now if the Samaritan may knead dough in an Israelite's house, it is evident the Israelite might use the Samaritan.

"An Israelite may circumcise a Cuthite; but a Cuthite may not circumcise an Israelite, because he is circumcised into the name of mount Gerizim. R. Josah saith, Let him circumcise him, and let him pass into the name of mount Gerizim till he departs this life." If therefore it was lawful for the Israelite to circumcise the Cuthite or Samaritan, and the Samaritan the Israelite, then the Jews had dealings with, or did use, the Samaritans...

"For three days before the feasts of the idolaters, it is forbidden [the Jews] either to give to or receive from them, to ask, or lend, or borrow of them": but for any other parts of the year it was not forbidden them. But as to the Samaritans, it was not permitted the Jews to borrow or receive any thing from them at any time gratis. Whereas it was lawful for the Jews to converse with the Samaritans, buy of them, use their labour, answer to their benedictions, 'Amen,' as we find in Beracoth, lodge in their towns, Luke 9:52, I would fain know in what sense, after all this, can it be said, For the Jews have no dealings with the Samaritans, but in this only, that they would not be obliged to them for any kindness? which may a little serve to illustrate that of Luke 10:33, &c.; and it does very well agree with the matter in hand.

For the words which we are handling seem to be what the woman speaks, and not what the evangelist: and they spokescoptically, or with sarcasm; "Dost thou, who art a Jew, ask water of me, who am a Samaritan?" for you Jews despise all courtesy of the Samaritans to receive the least kindness of them; and do you ask me for water?