Origen

(in Joh. tom. vi. c. 6) John, as it appears, saw from the question, that the Priests and Levites had doubts whether it might not be the Christ, who was baptizing; which doubts however they were afraid to profess openly, for fear of incurring the charge of credulity. He wisely determines therefore first to correct their mistake, and then to proclaim the truth. Accordingly, he first of all shews that he is not the Christ: And he confessed, and denied not; but confessed, I am not the Christ. We may add here, that at this time the people had already begun to be impressed with the idea that Christ’s advent was at hand, in consequence of the interpretations which the lawyers had collected out of the sacred writings to that effect. Thus Theudas had been enabled to collect together a considerable body, on the strength of his pretending to be the Christ; and after him Judas, in the days of the, taxation, had done the same. (Acts 5) Such being the strong expectation of Christ’s advent then prevalent, the Jews send to John, intending by the question, Who art thou? to extract from him whether he were the Christ.