Albert Barnes on John 4:25

I know that Messias cometh. As the Samaritans acknowledged the five books of Moses, so they expected, also, the coming of the Messiah.

Which is called Christ. These are probably the words of the evangelist, as it is not likely that the woman would explain the name on such an occasion.

Will tell us all things. Jesus had decided the question proposed to him (Jn 4:20) in favour of the Jews. The woman does not seem to have been satisfied with this answer, and said that the Messiah would tell them all about this question. Probably she was expecting that he would soon appear.