I was meditating (on "worship in spirit and truth" ) when I came across the story of Jesus and the woman at the well; what's the cause of the hatred between Jews and Samaritans?

The samaritans are also Israelites but their ancestors began to worship other Gods in the Old testament hence the dislike of the Jews for them.

Docjay487:

I was meditating (on "worship in spirit and truth" ) when I came across the story of Jesus and the woman at the well; what's the cause of the hatred between Jews and Samaritans?

The Samaritans were a group of displaced Gentiles who lived in the area of central Palestine. They were originally idolatrous and burnt their children in the fire (2 Kings 17:31). The Samaritans who were mostly of Gentile background with a mixture of Israeli blood who had become adherents of a quasi-Jewish religion that was also part pagan.

They were also Israelites who had inter-married with local pagan tribes and were seen as semi-Jews. The Jews hated them and would have no dealings with them (John 4:9).

Samaritans today are what I would call the "Christians" who have married the pagan ideologies with biblical doctrines and thereby have become quasi-Christians.