Jesus and the disciples "left Judea and went away again to Galilee. And He had to pass through Samaria" (v3-4).

Jesus sent the twelve disciples out at the beginning of his ministry instructing them, saying, “Do not go on a road to Gentiles, and do not enter a city of Samaritans; but rather go to the lost sheep of the house of Israel" (Matthew 10:5-6). This preaching to the Jew first and then non-Jew was a practice also followed by the Apostle Paul later on. By the time recorded in John 4, Jesus specifically goes out of his way to pass through the land of Samaria.

"The pregnant phrase to underline in the incident at Sychar’s well which is so rich in spiritual instruction, is the announcement John gives at the beginning of the chapter, namely, “He must needs go through Samaria.” Why the necessity? While this was the shortest and most usual road for a traveler going from Galilee to Jerusalem (Luke 9:52), the Pharisees avoided this customary route, and took a longer, round-about one through Peraea. They did this in order to avoid any contact with the Samaritans with whom, as Jews, they had no dealings. While the Jews and the Samaritans were physically alike in many ways, requiring the same food, following the same occupations, having the same hopes and ambitions, and suffering the same diseases, yet there was a racial hatred that kept them apart."
Lockyer's All the Women of the Bible

Jesus said to the woman "...whoever drinks of the water that I will give him shall never be thirsty; but the water that I will give him will become in him a fountain of water springing up to eternal life" (v14). 

God in Jeremiah 2:13 declares that he is "The fountain of living waters". This is repeated again in Jeremiah 17:13 "fountain of living water, that is the Lord"

Jesus in John 7:37-38 stood and cried to the children of Israel, “If anyone is thirsty, let him come to Me and drink. The one who believes in Me, as the Scripture said, ‘From his innermost being will flow rivers of living water.’”

The people of Samaria said "we have heard for ourselves and know that this One truly is the Savior of the world" (v42).

Here is a reminder of the promise made to Abraham in Genesis 12:1-3 that "in you all the families of the earth will be blessed". God's promise has always encompassed both Jew and non Jew. 

If we take on Christ through belief, changed life and then baptism, "then you are Abraham’s descendants, heirs according to promise" (Galatians 3:.27-29)