1:21 And they asked him, What then? Art thou Elias? And he saith, {i} I am not. Art thou {k} that prophet? And he answered, No.
(i) The Jews thought that Elias would come again before the days of the Messiah, and they took as the basis of their opinion Mal 4:5, which is to be understood as referring to John, see Mt 11:14. And yet John denies that he is Elias, answering their question just as they meant it.
(k) They are inquiring about some great prophet, and not about Christ, for John denied before that he is Christ, for they thought that some great prophet would be sent like Moses, using to support this position De 18:15, which is to be understood to refer to all the company of the prophets and ministers, which have been and shall be to the end, and especially of Christ who is the head of all prophets.
1:20,21 He confessed, etc. Some conjectured that John was the expected Christ; others that he was Elijah who was first to come (Mal 4:5); others that he was that prophet, the one predicted by Moses (De 18:15); but he declared that he was none of these.
1:21 Art thou Elijah? - He was not that Elijah (the Tishbite) of whom they spoke. Art thou the prophet - Of whom Moses speaks, Deut 18:15.
1:19-28 John disowns himself to be the Christ, who was now expected and waited for. He came in the spirit and power of Elias, but he was not the person of Elias. John was not that Prophet whom Moses said the Lord would raise up to them of their brethren, like unto him. He was not such a prophet as they expected, who would rescue them from the Romans. He gave such an account of himself, as might excite and awaken them to hearken to him. He baptized the people with water as a profession of repentance, and as an outward sign of the spiritual blessings to be conferred on them by the Messiah, who was in the midst of them, though they knew him not, and to whom he was unworthy to render the meanest service.