John Gill Commentary John 4:17

"The woman answered and said unto him, I have no husband. Jesus saith unto her, Thou saidst well, I have no husband:" — John 4:17 (ASV)

The woman answered and said, I have no husband
Which was a truth she would not have spoken at another time or place, or to any of her neighbours.

But Christ being a stranger, and no odium incurring upon her by it, and this serving a purpose to excuse her going to call him, she declares the truth of the matter:

Jesus said unto her, you have well said, I have no husband ;
this is the truth, it is really fact, and is the true state of the case, between you and him, who goes for your husband.