Come and see translates a Greek expression different from the one used in 1.39, but the force is the same.

The woman’s question Could he be the Messiah? implies a degree of doubt on her part, though perhaps mixed with hope. The same type of question is used in 7.26. In 18.35 and 21.5 it is also used, but with the implication that the assumed answer is “No.” Could he be the Messiah? may be rendered “Is it possible that he may be the Messiah?” or “Do you think that he is the Messiah?” Here the question does not concern the potentiality of Jesus to be the Messiah, but rather the matter of probability. In this context a question implying doubt would be more effective in getting people to come and listen to Jesus than would an expression suggesting complete assurance. A statement of assurance would merely have stimulated controversy, rather than serious inquiry.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .