Albert Barnes Commentary John 4:20

"Our fathers worshipped in this mountain; and ye say, that in Jerusalem is the place where men ought to worship." — John 4:20 (ASV)

Our fathers. The Samaritans; perhaps also suggesting that the patriarchs had done so as well. (Genesis 33:20).

Worshipped. That is, they had a place of worship.

In this mountain. This refers to Mount Gerizim, just a short distance from Sychar. On this mountain, they had built a temple somewhat similar to the one in Jerusalem. This was one of the main subjects of controversy between them and the Jews.

The old Samaritan Pentateuch, or the five books of Moses, has the word Gerizim instead of Ebal in Deuteronomy 27:4. For this reason, and because the patriarchs are mentioned as having worshipped in Shechem, they supposed that this was the proper place to erect the temple.

You say. That is, you Jews.

In Jerusalem. This refers to the place where the temple was built. It was built in accordance with the promise and command of God (Deuteronomy 12:5, 11). In building this temple, David and Solomon were under divine direction (2 Samuel 7:2, 3, 13; 1 Kings 5:5, 12; 8:15-22).

Since it was intended in the Law of Moses that there should be only one place to offer sacrifices and to hold the great feasts, it therefore followed that the Samaritans were in error in supposing that their temple was the place. Accordingly, our Saviour decided in favour of the Jews, yet in a way that showed the woman that the question was of much less consequence than they supposed it to be.