Albert Barnes on John 4:16

Go call thy husband. We may admire the manner which our Saviour took to lead her to perceive that he was the Christ. His instructions she did not understand. He therefore proceeded to show her that he was acquainted with her life and with her sins. His object, here, was to lead her to consider her own state and sinfulness--a delicate and yet pungent way of making her see that she was a sinner. By showing her, also, that he knew her life, though a stranger to her, he convinced her that he was qualified to teach her the way to heaven, and thus prepared her to admit that he was the Messiah, Jn 4:29.