Student or Learner
22 You Samaritans know very little about the one you worship, while we Jews know all about him, for salvation comes through the Jews.
For can be used in the following ways:
as a preposition (followed by a noun): I bought some flowers for Chloe. ♦ Wait there for a while.
as a conjunction (connecting two clauses): I told her to leave, for I was very tired.
used for talking about reasons or causes
as a result of something He was sick for lack of food.
We're all much better people for having known Carl.
for - definition. American English definition of for by Macmillan Dictionary
As you see, I have checked the dictionary, and found that for can be functioned as preposition or conjunction. So, I think that for in the quoted verse is conjunction. However, I couldn't grasp the exact meaning of for in that verse. Does it mean "as a result"?
It's more like a "because."