Gann's Commentary on the Bible

Samaritans -- After Assyria conquered the northern kingdom of Israel in 722 bc and deported most of its people, Samaria was inhabited by a mixed population. This included Israelites left behind after the deportation and foreign peoples relocated to the region from other parts of the Assyrian Empire (2 Kings 17:24-41). Those groups intermarried and thus a distinctly Israelite identity in Samaria was lost, forming the people group the Samaritans. However, like the Jews, Samaritans worshiped Yahweh and used a version of the Pentateuch as their Scripture. Jews and Samaritans typically had a mutual hostility based on ethnic, religious, and political barriers. See note on Luke 10:33. - FSB

Jews have no dealings with Samaritans -- The woman was surprised that Jesus would speak to her, much less ask her for a drink. This parenthetical comment is added for the benefit of John’s non-Jewish readers.

[Only the Apostle John supplied information bilingually in the New Testament (cf. John 1:38, John 1:42; John 4:25; John 6:1; John 9:7; John 11:16; John 19:13, John 19:17, John 19:20; John 20:16; Revelation 1:7; Revelation 3:14; Revelation 9:11; Revelation 12:9).]

John 4:29