Ye worship ye know not what - This probably refers to the comparative ignorance and corruption of the Samaritan worship. Though they received the five books of Moses, yet they rejected the prophets, and of course all that the prophets had said respecting the true God. Originally, also, they had joined the worship of idols to that of the true God. See 2 Kings 17:26-34. They had, moreover, no authority for building their temple and conducting public worship by sacrifices there. On all these accounts they were acting in an unauthorized manner. They were not obeying the true God, nor offering the worship which he had commanded or would approve. Thus, Jesus indirectly settled the question which she had proposed to him, yet in such a way as to show her that it was of much less importance than she had supposed.
We know - We Jews. This they knew because God had commanded it; because they worshipped in a place appointed by God, and because they did it in accordance with the direction and teaching of the prophets.
Salvation is of the Jews - They have the true religion and the true form of worship; and the Messiah, who will bring salvation, is to proceed from them. See Luke 2:30; Luke 3:6. Jesus thus affirms that the Jews had the true form of the worship of God. At the same time he was sensible how much they had corrupted it, and on various occasions reproved them for it.