Jesus means that God revealed himself and his commands to the Jewish people, not to the Samaritans. Through the scriptures the Jewish people know who God is better than the Samaritans.
## for salvation is from the Jews ##
This does not mean the Jewish people will save others from their sins. It means God has chosen the Jews as his special people that will tell all other people about his salvation. AT: "for all people will know about God's salvation because of the Jews"