John Gill Commentary John 4:26

"Jesus saith unto her, I that speak unto thee am [he]." — John 4:26 (ASV)

Jesus says to her
Upon her making mention of the Messiah, of his coming, and of his work, he took the opportunity of making himself known to her:

I that speak to you am [he] ;
the Messiah; see (Isaiah 52:6) . This is a wonderful instance of the grace of Christ to this woman, that he should make himself known in so clear and plain a manner, to so mean a person, and so infamous a creature as she had been: we never find that he ever made so clear a discovery of himself, in such express terms, to any, as to her, unless it were to his immediate disciples; and these he would sometimes charge not to tell who he was.